Abstract: The structural system of nappe consists of several overthrust fracture
belts，thrust sheets and thrust slices，and master fault and secondary fault
form an imbricate structure.This paper desdfibesin detail the characteristic,
of four master thrusts, and thrust sheets ira between and frontal zone，
and studies the development and formation mechanism of the thrust nappe by field observation and by simulated test of mud materials indoor.It has been pointed out that the frontal triangular zone is the most favourable exploration region of oil and gas.

Key words: Overthrust nappe, Master thrust fracture belt:Thrust sheet:Frontaltr