Aimed to the building mode of AP1000 nuclear power plant and the special features of poor working environment of equipment, high corrosion resistance and non-replacement of equipment after commissioning, the application of S32101 duplex stainless steel in AP1000 nuclear power plant was discussed. Besides, the chemical compositions, microstructure, welding characteristics of duplex stainless steel were introduced, and its welding process, the key control points of welding was also suggested.