Abstarct: The aim of petrophysical studies is the reservoir formation zoning, determination of net pay zones, and, finally, investigation of the reservoir quality of in different parts of the reservoir formation, and therefore, to determine the most suitable zones for optimal production from the reservoir and for more expert development of the hydrocarbon field. Porosity, water and hydrocarbon saturations, and permeability are the most important parameters that should be determined in petrophysical assessment to understand the reservoir quality. The purpose of this study is to determine the reservoir quality in different zones of Kangan and Dalan reservoir formations in a well located at one of hydrocarbon fields in south of Iran. This study was performed to evaluate the reservoir petrophysical characteristics of Kangan and Dalan formations. For this, petrophysical evaluation of these formations was carried out using multimin method in Geolog software. The multimin method is baxsed on probabilistic and geostatistical techniques. In this study, the effective parameters on the reservoir quality comprising of porosity, permeability and water saturation were selected. Then, the effect of each of the parameters on the reservoir quality was investigated, and as a result, a new index or formula, called developed reservoir quality index (DRQI), was introduced. baxsed on the importance of each of these parameters in the introduced reservoir quality, different values were selected for the coefficients A, B, C, and powers α, β and γ in the formula, and consequently, the best values of these coefficients and powers were obtained by plotting the DRQI in terms of water saturation, and maximizing the amount of regression or determination coefficient. In order to determine the validity of the formula introduced as the DRQI for other reservoir formations having different lithologies, this formula was used for the Sarvak carbonate formation in an oil field, and also, for the Burgan sandstone formation. As a result, Different values were obtained for these coefficients and powers in the formula. The values of the developed reservoir quality index for zones K1 and K2 of the Kangan Formation is 45.1 and 6.06, respectively, and for zones K3 and K4 of the upper Dalan Formation is 15.48 and 20.38, respectively. The results of this study indicate that the zone K2 of the Kangan Formation and the zone K4 of the upper Dalan Formation have an appropriate reservoir quality in terms of the DRQI. Finally, to determine the priority of the reservoir zones in terms of the reservoir quality, the methods of Sogeno and Choquet fuzzy integrals were used. The results of both methods are generally in agreement with each other. However, these results are associated with risk and uncertainty. The final results showed that the zone K2 of the Kangan formation and the zone K4 of Dalan formation like index introduced are in the first priority from the aspect of the reservoir quality.