Abstract: In order to improve the water conditions of acidic wastewater and complex wastewater after HDS process in tailings factory of Dexing Copper Mine and deal with the content of COD and some metal ions that exceed the emission standard, the treatments on those wastewater by nanofiltration are tested under the conditions of temperature of 30 ℃, feed pressure of 1.5 MPa and membrane flux of 16~18 L/min. It is found that membrane flux shows a trend of decline with the increase of nano-filtration concentration times. After four nano-filtration concentration times, the membrane flux of acidic wastewater is reduced from 70.06 L/(m²·h) to 21.86 L/(m²·h). After five nano-filtration concentration times, the membrane flux of complex wastewater is reduced from 103.14 L/(m²·h) to 39.99 L/(m²·h). SS, COD, Cu, S^2-, Zn, Pb contained in both of acidic wastewater and complex wastewater have reached the existing enterprise emissions standards. After the experiment, the flux of nano-filtration membrane has basically restored to the original membrane flux by cleaning the membrane in the conventional methods.