Abstract: Bainiuchang Ag-polymetallic Deposit is located at the central polymetallic ore belt of Southeast Yunnan， the associated mineral resources reserves of Ag，Sn，Pb and Zn are of the deposit are large or super large scale，and it is accompanied by abundant disperse elements.Due to the genesis of the deposit is controversial，further exploration and development are restricted.According to the S isotopic compositoin of Bainiuchang Deposit is systematically studied based on the latest s isotopic data of the ore minerals of the new mining section of the deposit.The study results show that the variation scope of the δ34S values of ore minerals of Bainiuchang Deposit is small，δ34S value for pyrite is from 2.5‰ to 4.0‰，δ34S value of pyrrhotite is from 2.7‰ to 3.9‰， δ34S value of sphalerite is from 2.9‰ to 4.3‰， δ34S value of galena is from 1.5‰ to 2.3‰， δ34S value of chalcopyrite is from 3.4‰ to 4.3‰.By the comparision of the δ34S values of the sulfides from ore-hosting strata and granite，it is show that the sulfur in Bainiuchang Deposit is mainly derived from magmatism，it belongs to magmatic hydrothermal deposit.Based on recently geological study results of Gejiu and Dulong polymetllic deposits， it is show that granitoids of Late Cretaceous and its periphery area are the favorable locations for the prospecting areas for polymetllic deposit in Southern Yunnan Province.

Key words: Ag-polymetallic deposit, Sulfur isotopic, Magmatism, Magmatic hydrothermal deposit, Prospecting prospective