The micro-Doppler signature is one of the most prominent information for target classification and identification. As Hough transform (HT) is an efficient tool for detecting weak straight target traces in the image, an HT based algorithm is proposed for micro-Doppler signature separation of multiple persons. Few seconds data is processed at one time to ensure human motion traces approximate to straight lines in the radar slow time-range image. Taking HT to the slow time-range image, each human’s motion trace can be recovered through recursively searching the peaks in HT space. Applying time-frequency transform to the range cells around each recovered line, the human micro-Doppler signature can be achieved and separated. Experimental results are given to illustrate the validity of the proposed algorithm.