Abstract: S20433 austenitic stainless steel plate was welded by plasma arc welding, and the microstructure and properties of joints by post-weld air cooling and water cooling methods were studied. The results show that the ferrite content in the joint by water cooling method was higher than that by air cooling method, and the heat affected zone was narrower. The hardness of the joint by water cooling method was slightly higher than that by air cooling method. The tensile strengths of joints by air cooling and water cooling methods were 693, 667 MPa, respectively, and the joint by air cooling method had better strength matching with base metal. No cracks appeared in the joint by air cooling method after bending tests, but the joint by water cooling method cracked during root bend tests due to the presence of oxide inclusions, indicating that joints by air cooling method had better toughness. The joints by two cooling methods both had good resistance to hydrogen-induced cracking. The joint by post-weld air cooling method had better comprehensive performance.