Yitong Graben , located the middle of Jilin Province , is southern section of Jia—Yi Graben and the northern section of Tan—Lu Fault Zone. Its northern—west margin is principal fault, and southern—east margin is polarity compensation fault. Main controlling faults and prolonging basin make complexity of structure and sediment，and there are many little fault depression basins in the Yitong graben. Miliqing fault depression is one of mainly filling oil and gas secondary fault depression basins in Yitong graben, its sedimentary caprocks are Palaeogene system strata , and sedimentary systems include fan—delta sedimentary system and lacustrine subaqueous fan sedimentary system, oil and gas distributes in the difference sedimentary system of Shuangyang Formation. According to the core ,the well—logging and the seismic data,  the papermainly describes characteristics of subaqueous fans ,results of research show that subaqueous fan system and fan—delta sedimentary system are different in lithologic series ,well logging feature and seismic reflection structure . Based on the above we investigate distribution laws of subaqueous fans and fan—delta along with time and space . Inner fan, middle fan and outer fan of subaqueous fans have great change on the plane with time varying, but fan—delta of northern—west margin usually keeps constant in the plane; By the detailed analysis  ,we think that formation of lacustrine subaqueous fan is related with structure , provenance supply and lake level changing; It is main controlling faults that make a great deal of subaqueous fans develop in the Member Ⅱ Shuangyang Formation.  Provenance supply sizes determine the shapes of subaqueous fans in the space and time, the greater size of subaqueous fans are formed by the direct provenance provision and that of the smaller by indirect provenance provision.