Abstract:With the construction of global navigation satellite system (GNSS), the technology of multisystem fusion time comparison has become the developing trend in the field of timekeeping. In this study, the data of GNSS receivers are utilized, which are from the time keeping laboratories of National Time Service Center of Chinese Academy of Sciences, Institute of Photonics and Electronics Academy of Sciences of the Czech Republic, and SP Technical Research Institute of Sweden. Based on the multisystem measurements data and the precision products clock, orbit downloaded from the international GNSS service center, the multisystem GNSS data fusion technology in PPP time comparison is studied. Experimental results show that the multisystem fusion technology can increase the number of available satellites. Compared with the single system, the number of observed satellites is doubled. The effects of multipath error and observation noise are reduced, which are caused by observation altitude angel. The influence of receiver clock error is suppressed, which can be used to improve the stability and reliability of time comparison. With the multisystem GNSS fusion technology in the long baseline time comparison, the stability results are better than of the any single system. Compared with BDS, GLONASS and Galileo, the stability is increased by at least 5%. .txt