Abstract: The reference epoch based relative clock was estimated using the method of epoch-difference and satellite-difference.An experiment is carried out using the data of different sampling rates collected from Hong Kong and Shanghai GNSS reference networks,in order to study the influences of region and sampling rates to the accuracy.The results show that the difference between our results and IGS final precise clock error products is less than 0.2 ns,and the accuracy of the reference epoch based relative clock is less than 0.9 ns.The accuracy is at the same level in different regions,and the influence of sampling rate is very small.