This study focused on preparing drinking water from the tidal salty water of Qiantang River by nanofiltration technology. Some commercial nanofiltration membranes were compared and the performance of optimized membrane was measured. A nanofiltration pilot-scale system with 500 m3/d was operated and optimized. The results showed that it was effective in removing the salt and reducing the organic pollutants from tidal water for nanofiltration technology, and nanofiltration could play an important role of security for drinking water.