Spacecraft sealed cabin contains hundreds of resistance spot welding. It’s ultra important to ensure the joint quality through monitoring and controlling the nugget size as well as metallurgy defeats. In order to monitor the spot welding quality of spacecraft sealed cabin,an on-line spot welding monitoring and quality assessment system is developed. Through the statistical analysis of the collected original characteristic information,the eigenvalues of the pressure curve and the dynamic resistance are obtained,and the online assessment of the quality of solder joint spatter,virtual solder joint（or solder joint nugget）is achieved. Verification results show that the system has high credibility. The system has been successfully applied to monitor the welding production of cabin reinforcement ribs. This research might provide some advises to the building of spacecraft digital workshops,and can also improve the ability of quality monitoring and digital traceability during the manufacturing of spacecraft.