Abstract: Welding procedure qualification is an essential part of quality control for welded ship.Expert system of welding procedure qualification with knowledge management and expert reasoning based on web environment is established.The entire process management of data and processes in the process of ship welding procedure qualification is achieved.It is of great significance for enhancing the technical level of ship welding procedure qualification and promoting the construction of enterprise information.The overall design,functional structure,establishment of process knowledge base and expert reasoning of the system are discussed in this paper.