In radar target detection application fields, rich of information of targets may be included in medium frequency. Doppler shift caused by moving target is one of them. In this paper, Doppler shift and its Short Time Fourier Transform-STFT is analyzed and discussed. Since it is difficult to distinguish the Doppler shift of moving target even in frequency domain with STFF method, fuzzy C means clustering method is introduced to seek the two centers of the mixed signals in a radar scanning period. Using multiple radar scanning period, several centers can be determined by a center function using arithmetic mean filter. Finally the targets can be detected by threshold decision and calculated the detection probability. This algorithm is simple, easily to realize, with small computation burden and good target detection probability.