Abstract: Precise point positioning (PPP) was originally developed for positioning and navigation applications. Recently it has gradually been accepted as an effective tool for non-positioning applications such as time transfer. Nowadays, more and more stations use the high stability Hydrogen atomic clock to provide datum of time and frequency. However, receiver clock offsets are generally regarded as white noise parameters in customary PPP time transfer method, which does fully utilize the high stability of Hydrogen masers. Therefore, we calculate the empirical variance of H-masers based on real GPS observations, and proposed a constraint method of receiver clock offsets between adjacent epochs to improve the performance of PPP time transfer. We confirm this model by three time links experiment. The results imply that, compared with the customary PPP time transfer method, our method has higher stability and the short-term stability can increase up to one order of magnitude.