Shaft rate magnetic field signals produced by the unmanned helicopters in maneuver flight is an important physical fields, which is difficult to be stealth. Unmanned helicopters can be detected and identified by analyzing the shaft rate magnetic signal, and the status of the unmanned helicopters can be monitored. In this paper, the magnetic field sensors are used to detect the shaft rate magnetic field signals of the unmanned helicopters. Short time Fourier transform for timefrequency analysis is applied to deal with the measured data. The testing results show that the specific shaft rate magnetic field signals of 5~40 Hz which are related to unmanned helicopter’s status are generated in unmanned helicopters maneuver flight. According to the characteristics of the signal, detection and identification of unmanned helicopters are realized. The detection method has a good effect in the real data application.