Abstract: Imageries of structures in Sichuan basin clearly show that there exist different types of traps in the basin,characterized,vertically,by a general disconcordance in their configuration,location,size and elevation.A lot of work has been done and some knowledge has been gained about this phenomenon,but the effort made in the analysis of the types of and mechanism for the vertical variations of structures in the basin is far from being adequate.As the latter problem has a most important bearing oz the appraisal of oil and gas prospect and planning of exploration activities for the basin,a close study of the subject is warranted.This paper is written on the basis fo experiments in petro-mechanics of the overburden in Sichuan basin(test data of over 800 pieces of rock samples) and seismic profiles of nearly a hundred local structures in the basin,coupled with geological,geophysical and aeromagnetic data,with the conclusion that the texture of the metamorphosed basement,composition of overburden,paleo-structures and their boundary conditions are factors affecting the vertical variations of structures.