The trace of a listric normal fault can be calculated by using the method of regression analy- sis and constructing a mathematical model．Interrelated coefficients of calculated profiles are more than 0．97．The formation of listric normal faults in the Jiyang depression has relationship with the following 4 factors：(a)existence of a ductile layer，(b)compaction，(c)rotation of fault— block and(d)erosion of steep banks by lake water．Lithologic traps in the form of subaqueous fan along the listric normal fault，which are controlled by the dip of the listric normal fault，dis— appear when the dip is about 20。