In order to improve the accuracy of gesture recognition, we investigate the feasibility of using a three-dimensional Doppler-radar array at 24GHz to recognize human gestures with a model consisted of ten classical gestures. On the basis of C4.5 algorithm, phase difference and spectral energy, extracted by correlation processing and power integral, are used as the features to construct decision tree and separate ten gestures. The experiment result shows that this system could achieve a high accuracy of classification reached 99.25%.