By analyzing petrology characteristics in detail and combining the regional background, the origin of Middle Triassic Leikoupo gypsum and salt rocks in Sichuan basin was studied,which revealed the gypsum and salt basin’s migration and evolution that’s significant for reconstructing tectonic background.There were two kinds of gypsum and salt rocks with different lithology association and distribution characteristics , one of which caused by lagoon environment existed in Lei11-Lei31 period, when there appeared laminated gypsum and salt rocks interbedded with blocky gypsum and salt rocks whose thicknesses were small and lateral distributions were stable. And the other of which caused by gypsum and salt basin environment existed in Lei32-Lei42 period, when there mainly appeared blocky gypsum and salt rocks whose thickness difference were great and lateral distributions were not stable. This kind of gypsum and salt rocks’ depositional central had such tendency of migration towards West and North,which had sharp contrast to the gypsum and salt rocks caused by lagoon environment.Tectonic information could be inferred by the above that Middle Triassic Leikoupo tectonic stress field was converted from extensional stress to extruded stress.Lei1-Lei31 was a tectonic calm period,which belonged to a transitive period from extensional stress to extruded stress. In comparison, Lei32-Lei42 was a tectonic active period, when extruded stresses in direction of Westnorth-Eastsouth and Eastnorth-Westsouth became so active that new subsidence central formed, where gypsum and salt rocks deposited rapidly in the depression controlled by intense evaporation. There existed three stages gypsum and salt basins of Lei32,Lei33,Lei41-2 ,which had the tendency of migration towards North and West as the result of active tectonic extrusion in stage. West Sichuan depression began developing in Lei32 period, and had initial shape in Lei41-2 period.These thoughts provided new informations for studying the origins of Leikoupo gypsum and salt, Sichuan basin, and provided an idea of revealing tectonic information by depositional analysis.