Based on data obtained from the Chengmenshan porphyry copper deposit in Jiangxi and the Wunugetushan porphyry copper deposit in Inner Mongolia, the authors investigated the petrochemical indices for the exploration of porphyry copper deposits. It is shown that the contents of such common chemical components as MgO, CaO and Na2O are obviously lower than their abundances in immediateacid rocks, whereas w(Na2O)/w(K2O) and w(CaO)/w( MgO) ratios vary regularly with the increasing Cu mineralization intensity. These results can effectively indicate the existence of porphyry mineralized bodies and their mineralization intensity and greatly enrich the geochemical exploration indices.