Targeting at mutual disturbance caused by multiple signals and difficult modulation identification under the circumstances of time-frequency overlap, an identification method based on high-order cumulant is raised. There exist high-order cumulant divergences of different digital phase-modulated signals, and high-order cumulant is not sensitive for noises. By taking advantages of these two characteristics and selecting four feature parameters, classification method of decision tree is adopted to undertake pattern identification of ten types of phase-shift keying three signals. The experiment results show that, under the circumstance that noise-signal ratio is not less than 0dB, ten types of time-frequency overlapping three signals can be identified effectively. This algorithm not only improves the signal identification rate, but also increases the numbers of identical time-frequency overlap signals.