This study was prepared to identify and rank all factors contributing to the occurrence of marine accidents of vessels with gross tonnage less than 500 (Khuzestan waterways study) for the first time. The findings of this research can be used to adoption effective practical measures to improve the safety level of vessels with gross tonnage of less than 500 which traffic in Khuzestan waters. In this study, in addition to library and documentary study, a questionnaire was used to collect data. Descriptive and inferential statistics were used for data analysis and SPSS and Expert choice statistical software were used for data processing. Based on the analysis and results, human factors, environmental factors, software factors and hardware factors influence the occurrence of vessels with gross tonnage less than 500 in Khuzestan waterways, of which a human factor with a final weight of 0.534 is the highest priority than other factors. Also among sub-factors, defect and lack of training of ship personnel among human sub-factors, factor of natural channel characteristics (severe flow of water, depth and width) among sub-environmental factors, lack of proper implementation of existing technical and safety guidelines among the Software factors and maintenance factors of hull and equipment of vessels among the hardware factors are the first priority over other sub factors.