Abstarct: Gravity method is one of the geophysical methods that can be applied in oil reservoirs preliminarily exploration, identification the geological features, subsurface structures and depth of the sedimentary basins. Separating the gravity data to the residual and regional components gives useful information about the main geological structures in the interested area under investigation, the geological and tectonic events occurred in the sediment basin and hydrocarbon potential of the region. Studying the methods that analyze the exploration data and their variations and give more reliable information about the geological structures is an essential task. In this study, the Dehno gravity data located at southwest Iran, are interpreted and modeled to better identify the Dehno anticline and its subsurface extension. The common anomaly separation methods including trend surface analysis, filtering and analytical methods are carried out using Modelvision Pro and Winglixnk softwares. The residual maps plotted from these methods show two positive anomalies A and B and negative anomalies C, D and E and anomaly F that can be related to the surrounding outcrops. After identifying the structures of the area and determining the geological sources of the anomalies, two and three dimensional (2D and 3D) modeling are carried out on the residual anomaly map associated with the order 3 of the trend surface method in order to determine the geometry and the physical properties of the geological structures. The results of 3D modeling determine the type of the structures, a low depth for positive anomalies A1, A2 and B and high depths for negative anomalies D1, D2 and D3; describing an increase in depth of the sedimentary basin to northwest parts. Anomaly A1 with a depth about 1406 m and dimensions 7515 14008 meters, anomaly A2 with a depth about 1073 m and dimensions 6199 11860 meters and finally anomaly B with 1235 m depth and dimensions 9612 1150 meters were detected baxsed on the 3D modeling results. The gravity data of the study area was also separated by applying modeling of the probability plot of gravity data for the first time that is baxsed on the data variations analysis on the modeled probability graphs. The boundaries of the residual and regional effects were completely separated according to the different variation slopes. The boundary of the mixed regional and residual effects was finally identified. The optimum residual anomaly map resulted from the modeling of the probability plots has separated the Dehno anticline (A anomaly) from the adjacent anomalies with more details. T- Student test was used for comparison of the anomalous areas detected by trend surface and the modeling of the probability graph which has shown a high correlation between the residual maps obtained by this two methods in identification the Dehno anticline and oil trap structures in this study area.