Aiming at the problem of increasingly scarce spectrum resources in the modern digital communication system, the spectrum characteristics and error performance of continuous phase modulation signals were discuss in this paper. First of all, the general form of CPM signal with three kinds of phase pulses is presented respectively, and the power spectrum density distribution of the modulated signal is obtained. And then, based on the minimum Euclidean distance, error performance of three kinds of CPM signals is studied. Simulation results show that: the CPM signal with Gauss′s minimum frequency shift keying pulse has more prominence both on spectral characteristics and the error performance compared with the other types. In practical engineering, choose applicable phase pulse modulation method according to the objective requirement. Finally, the system can get a reasonable compromise between validity and reliability.