With the successful launch of the 16 MEO satellites of the Beidou-3 global satellite navigation system and the broadcast of new signals, Beidou officially entered the global construction stage, while the international GNSS monitoring and assessment system (iGMAS) is also performing systematic testing and evaluation on various aspects of operational performance from satellite end to ground receiving end of Beidou-3 system. This paper analyzes and evaluates the observation quality of new signals B1C and B2a broadcasted by the 12 new Beidou-3 MEO satellites on the observation data integrity rate, multipath error, pseudorange noise and carrier-to-noise ratio (CNR) compared with GPS and GALILEO. The results show that the observation data integrity rate of B1C signal is better than that of B2a signal in the Beidou-3 system. In the aspects of multipath error, pseudorange noise and CNR, B2a signal are better than B1C. The performances of the 12 MEO satellites of Beidou-3 are equivalent, that is, Beidou-3 the consistency of satellites can be guatenteed. In terms of pseudo-range noise, Beidou-3 is slightly worse than GPS and GALILEO While the observation data integrity rate, multipath error and CNR of Beidou-3 are equivalent to GPS and GALILEO.