Abstract:The coordinated universal time offset(UTCO) parameter broadcast by the global navigation satellite system(GNSS) is updated with the modernization upgrading navigation systems. In particular, the UTCO parameters for GPS and BDS have been significantly changed. From the perspective of model, the first-order traceability model has been replaced with a second-order traceability model, compatible with the first-order model. From the perspective of resolution, the parameter resolution has generally decreased, improving sensitivity to small changes in UTCO. By investigating the UTCO parameters in the GPS LNAV messages, GPS CNAV messages, BDS D1/D2 messages, BDS B-CNAV messages, Galileo messages and GLONASS messages of the four major navigation systems GPS, BDS, Galileo and GLONASS, and based on the UTCr-UTC(k) data published by international bureau of measurement(BIPM), we integrate the GNSS UTCO parameters into the fast coordinated universal time(UTCr) to analyze the performance of UTCO parameters broadcast by various systems. Meanwhile, we adopt the time offset of GNSS system monitored by the national time service center(NTSC) and the circular T bulletin published by BIPM as references to evaluate the coordinated universal time offset error(UTCOE) of GNSS system. The results show that the UTCO parameters of GPS CNAV messages perform better than GPS LNAV messages, and the UTCO parameters of BDS B-CNAV messages perform better than BDS D1/D2 messages within the experimental period. The UTCO parameters of GPS and Galileo perform better than BDS and GLONASS, and BDS and GLONASS had some systematic errors in the UTC traceability.