The concept of inversion structure is discussed in this paper．Based on seismic exploration data of the Lishu depression of the Songliao basin，the characteristics of inversion structure and traps which are formed by inversion are presented．Their formation condition and identification features are，discussed in detail．It is believed that inversion structure is formed when an early— formed extensional or pull and pull apart basin underwent compression or compresso—shear in the late stage．The boundary fault which primarily was a synsedimentary fault was changed into a re— versed fault．The fault shows the features of a normal fault in the 10wer part and the features of a reversed fault in the upper part．During the process of inversion，an anticline with along axis was formed near the fault or in the main part．of the depressiom．This kind of anticline trap has special geological conditions，and often forms large oil and gas pools when other petroleum condN tions are favorable．