The west margin of Sichuan Basin is divided into the Longmenshan Range region and the Sichuan Basin region. The regionalizations presented by primary references consider that there is an apparent tectonic line between the both regions, which neglects different depositional environment and structural evolution between the autochthonous strata and the allochthonous strata along the west margin. A different regionalization is put forward that the apparent line does not exist between the two regions while the faults in the east of the three nappes that consist of the Longmenshan Range should be as the main line. It is proposed that Longmenshan Range region can be divided into three subregions and Sichuan Basin region into both the southwest and northwest subregions. The project of this regionalization is represented in detail.