The atomic clock is the core of the Global Navigation Satellite System (GNSS), which plays an important role in Positioning, Navigation and Timing (PNT) services. However, the long-term characteristics of the global BeiDou navigation system (BeiDou-3) and comparison of satellite clocks performance for the five GNSSs have not yet been revealed. We evaluated and analysed the performance of atomic clocks for BeiDou-3 and other GNSSs using satellite clock offset data. The important contributions are summarised as follows. (1) The phase and frequency sequences of Passive Hydrogen Maser (PHM) and rubidium (Rb) atomic clocks for BeiDou-3 are more stable and continuous than those of the regional BeiDou navigation system (BeiDou-2). The clock offset model precision and average frequency stability at 10,000, 1000, and 100 s for the BeiDou-3 satellite clock offsets are 0.15 ns and 6.8 × 10^–14, respectively, exhibiting significant improvements compared with those for BeiDou-2. (2) The performance of cesium (Cs) atomic clocks installed on Global Positioning System (GPS) Block IIF are more inferior than Global Navigation Satellite System (GLONASS), which may be due to the poor level of Cs atomic clock manufacturing technology or obvious noise characteristics. Thus, more attention should be paid to these two satellite clocks. (3) A comparison of various indicators revealed that the satellite clocks for Galileo are the best, followed by BeiDou-3, GPS Block IIF satellites with Rb atomic clocks, Quasi-Zenith Satellite System (QZSS), BeiDou-2, GLONASS, GPS Block IIR, and Block IIR-M. The GPS Block IIF satellites equipped with a Cs atomic clock shows the poorest performance.

原子钟是全球导航卫星系统（GNSS）的核心，它在定位，导航和计时（PNT）服务中发挥着重要作用。然而，全球北斗导航系统（BeiDou-3）的长期特性以及对五个GNSS的卫星时钟性能的比较尚未透露。我们使用卫星时钟偏移数据评估并分析了北斗3号和其他GNSS原子钟的性能。重要贡献概述如下。（1）北斗3号的被动氢Maser（PHM）和rub（Rb）原子钟的相位和频率序列比区域北斗导航系统（BeiDou-2）更稳定和连续。时钟偏移模型的精度和平均频率稳定性分别为10,000、1000，^–14分别比BeiDou-2有显着改善。（2）安装在全球定位系统（GPS）IIF块上的铯（Cs）原子钟的性能比全球导航卫星系统（GLONASS）差，这可能是由于Cs原子钟的制造技术水平低下或显而易见噪声特性。因此，应更加注意这两个卫星时钟。（3）对各种指标的比较表明，伽利略的卫星时钟是最好的，其次是北斗3号，带Rb原子钟的GPS Block IIF卫星，准天顶卫星系统（QZSS），北斗2号，GLONASS，GPS IIR块和IIR-M块。配备Cs原子钟的GPS Block IIF卫星表现最差。