Abstarct: The gravity method is used for detection of subsurface structures related to hydrocarbon resources in the first stages of exploration. The main purpose of interpretation techniques of the gravity anomaly in hydrocarbon exploration is to find those structures that could deserve the potential to be an oil trap. In this regard, there are varieties of qualitative methods that are able to discover such structures and to estimate their burial depth to some extent. The normalized full gradient (NFG) introduced at 1960, is one of these methods which is applied for the above purposes. It is also used to identify and clarify hydrocarbon bearing structures from dry ones. This method is baxsed on calculating the potential field function in form of some sine and cosine functions by Fourier series. Despite the ability of NFG method in recognition of potential field anomalies, especially in hydrocarbon resources exploration, there are still some not well defined parameters such as number of Fourier harmonic series (N), power of Lnacsoz smoothing function (µ), optimum length of profiles, dimension of exploration grid and spacing of measuring points that need to be determined to calculate NFG precisely. Additionally, this method and its capabilities have not yet tested for two and three dimensional (2D and 3D) salt dome exploration. Therefore, the optimum determination of the above parameters along side to introduce a criteria to identify oil traps related to hydrocarbon bearing salt domes and also providing an algorithm to calculate 2D normalized full gradient together with introducing a new 3D method for NFG calculation were selected as the main objectives of this research work. To achieve the goals, several different models that resembled an oil trap related to the anticline and salt dome structures were firstly made and their gravity response were then calculated by a sets of computing algorithms and codes prepared in the MATLAB programming environment. Following that with considering the appropriate NFG parameters, the required algorithms and programs to calculate NFG values for 2D and 3D structures were prepared and their capability also tested by some synthetic and real data. Due to natural 3D characteristics of geological structures related to oil traps, it was attempt to use double Fourier series to introduce a new method to calculate 3D normalized full gradient and its ability was tested by different sets of real and synthetic gravity and magnetic data. The obtained results indicate that the value of normalized full gradient is strongly depending on the optimized number of harmonic series to calculate the Fourier coefficients. This parameter so far was being determined baxsed on the complementary exploration data by trial and error procedure. In this study, a new method named relative maximum values of NFG as a function to the number of harmonic series, was introduced to determine this important parameter (N) without any complementary data. By considering such (N) value in calculating normalized full gradient of each profile and drawing its section, the horizontal position and depth of anomalous bodies could be preciously determined using relative maximum or minimum values of NFG. Another important parameter that influences the value of normalized full gradient value is the power of Lancsoz smoothing function that used to remove noise from data. The modeling done in this study shows that by introducing the values of 2 and/or 3 as the power of Lancsoz smoothing function, the best results would be obtained. The results show that if the length of the surveying profile is 13 times of the depth of the anomaly, and the space of the measuring points is designed half up to the full width of the expected buried anomalous body, the best accurate result would be obtained. Study on different models in one hand, showed that the value of density contrast does not affect on the number of harmonic series (N) and also the location of the minimum and maximum closed curves on NFG sections. Therefore if the effect of density contrast of an anomalous zone is recorded somehow, this method could adequately define their location. As it was expected, shape of the anomalous bodies has an effect on the number of harmonic series (N) and the location of relative maximum and minimum regions in a NFG section. The main advantage of the NFG method relative to the other methods of interpretation gravity anomaly is its capability in separation of the hydrocarbon filled traps from dry ones. The results of the present study indicate that the location of a salt dome or anticline structure containing hydrocarbon is manifested by a minimum closed lines that surrounded with two maximum closed lines in sections of the 2D normalized full gradient. In addition, these 3D oil traps filled by hydrocarbon are recognized in 3D normalized full gradient maps that are provided at different depth interval by minimum closed curves that enclosed by maximum lines. Therefore any presence of such minimum closed lines could be used as a criterion for hydrocarbon exploration. According to 3D nature most of the oil traps, it is attempt to develop the required mathematical relations to introduce a new technique for 3D normalized full gradient calculation by using double Fourier series. To verify the capability and the accuracy of the new introduced NFG methods in 2D and 3D cases, some gravity and magnetic data from different oil and gas field related to anticline or salt dome structures and also related data from mining exploration were then processed by these methods. Application of this method on the aforementioned real data sets proved the ability of this method on defining the horizontal position and depth of oil traps contain hydrocarbon or mineral resources. Additionally the obtained results by this method show good relations with drilling data for 2D and 3D anticlines or salt dome oil traps. The results of this study also show that 3D normalized full gradient provides more accurate results than 2D normalized full gradient and other pseudo 3D-NFG methods. This is due to simultaneous usage of Fourier series on both x-y directions in 3D normalized full gradient calculation. Therefore this method could be used to separate the oil and gas bearing traps from the other ones, to determine the locations of the exploratory drilling, and also to manage any further exploration activities.