Abstract: Space atomic frequency standard (AFS) is the key equipment of Global Navigation Satellite System (GNSS), and the performance evaluation of AFS has important value for navigation error analysis and optimization of space AFS.In this paper,the performance parameters of space atomic clock,the clock products of international GNSS monitoring and assessment system (iGMAS) were introduced.The frequency accuracy,daily drift and stability of space rubidium atomic clocks and passive hydrogen masers (PHM) on Beidou Navigation Satellite System (BDS) were evaluated and analyzed.The results show that the performance of BDS-3 AFS is significantly improved compared with BDS-2 AFS.The PHM has better long-term performance,10 days stability and frequency daily drift of which generally reach the order of 10^-15.