Abstract: S32101 duplex stainless steel plate with a thickness of 6.5 mm was welded by laser welding. The post-weld heat treatment at different temperatures (800-1 100 ℃) and different holding time (0-180 s) was carried out. The effects of post-weld heat treatment on the microstructure and properties of the weld were studied. The results show that the austenite content in the weld after heat treatment was higher than that of as-welded weld, its content increased with the extension of holding time, and increased first and then decreased with the increase of heat treatment temperature. The austenite volume fraction was more than 30% after the weld was held at 1 000-1 100 ℃ for 0-180 s, and the austenite volume fraction was the highest when the heat treatment temperature was 1 075 ℃. The average microhardness of the weld after heat treatment was lower than that of the as-welded weld and similar to that of the base metal. When the heat treatment temperature was 1 075 ℃,and the holding time was 0, the free-corrosion potential of the weld was similar to that of the as-welded weld. When the holding time was extended to 180 s, the free-corrosion potential increased, and the corrosion tendency decreased.