Abstract: The water supply scale of the Zhangjiagang Third Water Plant was 200000 m³/d, and its drinking water treatment process is sequentially combined by coagulation, sedimentation, filtration and chlorination disinfection. Based on the remarkable interception ability of nanofiltration membrane for monomolecular organic matters, micromolecular organic matters and saline ions including calcium ion, magnesium ion, sulfate ion, etc, a new water purification process combined by conventional technology, pressed-pot microfiltration and nanofiltrition was creatively applied in the large-scale engineering project of drinking water advanced treatment for the Zhangjiagang Third Water Plant, for the first time in China. The designed water production capacity of this project was 100000 t/d, and the project was aimed at upgrading the existing drinking water treatment technology. After the reformation, the nanofiltration system was predicted to perform over 90% removal rate for COD and TOC, 70%~80% removal rate for disinfection by-products, over 70% removal rate for pigments, 50%~70% removal rate for odorous substances, and 30%~40% rejection rate for salt. The recovery rate of the nanofiltration system was able to reach 90%, while the predicted energy consumption of pressed-pot microfiltration system and nanofiltration system was respectively 0.003, 0.197 kW·h/t, respectively. After accomplishing the project, Zhangjiagang Third Water Treatment Plant will be capable of supplying drinking water with higher quality, and possess higher resistance to water contamination emergencies.