Abstract: Reactor coolant pump (RCP) is the key equipment of nuclear power plants. This paper describes the structure, process and key technology for the assembling of the RCP.  The main factors affecting the progress and quality of the RCP assembling were found out by summarizing and analyzing the assembling problems. In addition, measures, such as strengthening the management of assembling plan, reasonably arranging the provision of labor, making good technical preparation before assembling and establishing emergency treatment channels, are taken to effectively improve the assembling quality and efficiency, which can provide experience reference for the RCP assembling in other nuclear power projects.