Abstract: By improving the satellites clock offset estimation method with epoch-differenced phase and un-differenced pseudo-range observations, we realize the estimation of GPS, GLONASS, BDS, and Galileo satellite clock offsets. Moreover 50 GNSS stations distributed worldwide were used to acquire multi-GNSS satellites clock offsets. Their precisions were analyzed. PPP was used to validate the estimated satellite clock offsets. The experimental results illustrate that the biases between satellite clock offsets as estimated and the final multi-GNSS precise satellites clock offsets generated using PANDA software package of Wuhan University were less than 0.2 ns. The PPP results using the estimated satellite clock offsets were close to the results estimated using the final multi-GNSS satellite clock offsets generated with the Wuhan University PANDA software.