Abstract: The Qishan Sn deposit is of post-magmatic hydrothermal infilling vein type, associated with the Yanshanian granite-porphyry. The ore bodies shape as veins and lens or compound of branches, with cassiterite-sulfide ores. The wall rock alteration involves greisenization, sericitization and chloritization. The study of the genesis of this deposit would provide a reference for searching of the ore deposits of the kind.