Located in central-west Inner Mongolia, China, Chaganhua porphyry molybdenum is a large scale deposit.  Geochronological and elemental data are presented for the ore-forming granites. The data show that the ore-forming granite was emplaced and crystallized in the Late Permian (253～254 Ma) . The major elements data show these granites are high K calc-alkaline series, metaluminous-peraluminous and characteristic of high silicon, high alkali. Combined with the trace elements features, it indicates that the ore-forming magmas is most plausibly originated by partial melting of previous subduction modified source, and has inherited some features of subduction related magma.