Abstract: Based on the conditions of the cryopump application in Beijing Institute of Spacecraft Environment Engineering, this paper establishes reliability models for cryopump tasks, and carries out the FMEA on the cryopumps. Upon collection and organization of the failure data of the cryopumps during the year 2009 to 2015, an estimation is given of the field failure rate and the MTBF in the form of histogram, and the reliability level of the cryopump in field use is assessed. In addition, based on the P-P theory of the lifetime distribution hypothesis, the lifetime distribution characteristics of the cryopumps are obtained. Based on the field reliability analysis and in light of the maintenance support experiences over the years, we provide relevant processes and methods for the maintenance of common failures of cryopumps in their subsequent use to ensure the continuous implementation of the thermal vacuum test.