The late Yanshanian magmatite in the Youjiang Fold Belt of West China is represented by basic-ultrabasic dyke swarms and ultra-acid rock veins. The new data support that the Yanshanian magmatic activity concentrated on 80~100 Ma in the Youjiang Fold Belt and the surrounding area, indicating large scale extension and lithospheric thinning in western China during the late Cretaceous. Since the granitic magmatic activity of late Cretaceous was related to a large scale Sn-(Cu-Pb-Zn) mineralization in western China, it is worth considering the prospecting potential for Sn-(Cu-Pb-Zn) in the area where quartz porphyry occurs within the Youjiang Fold Belt.