Abstract: BDS precise clock offset data from 2013-01-01 to 2018-05-01 are provided by WHU and GFZ. These data are used to evaluate the long-term performance of BD-2 on-board atomic clocks by phase, frequency, drift rate, frequency accuracy and stability. The results show that the phase data are not so continuous or stable and the phase modulations are frequent; the frequency drift rate maintains in 10-18-10-17/s; the frequency accuracy is stable in 10-11; the frequency stability in ten-thousands is about 10-14-10-13, and MEO satellites are more stable than GEO or IGSO satellites. Furthermore, according to the relationship between clock switching and frequency drift rate, accuracy and stability, the BD-2 satellite clocks switching information is verified and deduced.