Conventional Doppler signal recognition is mainly based on the amplitude of the Doppler signal. In the process of target recognition of sector beam detectors, this method has the problem of low recognition rate due to the narrowing of the Doppler time domain waveform. Based on the measured Doppler signal data, the time-frequency conversion analysis is carried out， and a signal recognition method based on combined judgment of frequency and amplitude is proposed without changing the existing beam shape. The experimental results show that the target can be identified accurately by the detector all the six times of the target entering the detection range, which provides reference value for UAV target recognition.