Abstract: The stability analysis of time offset between different satellite navigation systems is of great value in modeling prediction and application of time offset. Therefore, based on the data and products provided by the International GNSS Service Center (IGS), the stability analysis of system time offset between the GPS and BeiDou-3 Navigation Satellite System (BDS-3) from three aspects: different stations, different observations, and different time lengths. The results show: due to the different models of receivers, antennas and clocks, the time offset values extracted from different stations are different, but the stability is similar; The stability of the time offset result calculated based on the carrier phase observation is better than that of the pseudo range observation, the time offset result obtained by pseudo range has a frequency stability of the order of 10⁻¹² to 10⁻¹³ in 10 000 seconds, and the time difference obtained by phase has a frequency stability of 10⁻¹⁴ seconds. By comparing the time offset calculation results of single-day and multi-day data, it is obtained that the time difference stability of different durations is consistent.