Abstract: PCM/PPK telemefry system is a multiple-signal digital communication system whose structure is very simple. In this paper, utilizing the feature that codes transmitted by PCM/PPK are group codes, the bit error probability P_b is analysed and calculated under the various transmission stares, and the transmission error is analysed as the distribution of the prior probability is uniform. The results show that the PCM/PPK is very efficient telemetry system.