Abstract: On the basis of predecessors' research results,through comprehensive analysis of 15 coring Wells cores,well logging,sedimentary structure and field outcrop data,by adopting the principle and methods of sedimentology,the systematic analysis on sedimentary environment on Triassic Chang-7 oil reservoirs in Suijin area has been carried out.The results show that Chang-7 oil reservoirs belong to delta sedimentary system,and the delta plain subfacies have been mainly developed.Three sedimentary microfacies have been further classified:distributary channel,natural levee and split between depressions microfacies.Distributary channel and the natural levee microfacies have sand bodies of reservoir skeleton.At the same time,the research on spatial distribution characteristics of small layers of Chang-7 oil reservoir,namely Chang 71,Chang 72 and Chang 73 has been carried out.The results believe that the hydrocarbon accumulation is controlled by favorable sedimentary facies belt,the distributary channel microfacies and natural levee microfacies on the delta plain are the main oil and gas gathering places,and it is the further direction for oil and gas exploration and development in the next step.