Abstract: The Tuanshan ore block of Guanfang Pb-Zn-W orefield is located in Wenshan County of Yunnan Province, with medium tungsten orebody scale and medium-complex hydrogeological condition, including 3 aquifer formations. The main water source for pit filling is from the groundwater in the karst fractures within the roof and floor of orebody. The water inflow of the orefield is predicted with the big well method. The result shows that the normal water yields in the levels of 1200 m, 1300 m and 1400 m are 21587 m³/d, 9997 m³/d and 4484 m³/d, respectively, with the largest yields of 64761 m³/d, 29991 m³/d and 13452 m³/d, respectively.