Modulation type is one of the most important characteristics used in radar signal recognition. This paper proposes a method to realize modulation identification. This algorithm applies wavelet transformation to the signal, and then uses manifold learning method to reduce the high dimension and extracts the recognition feature. The proper threshold value is set as the classifier to achieve the purpose of recognizing 5 kinds of signals (2ASK, 2FSK, 2PSK, LFM, CP)in Gauss white noise environment. The algorithm requires priori signal information no other than signal-to-noise rate. Simulation result indicates the algorithm achieves good performance.