For the safety monitoring requirements of stereo garage, a machine vision based human detection algorithm is proposed to detect unlawfully intruded persons in the stereo garage. First, an adaptive bilinear filtering method is used to remove the noise of the video frame. Next, a difference image of the video frame and the background image is calculated, and the multi-scale wavelet analysis algorithm is employed to obtain binary image of the difference image. Then, human is detected from the binary image by morphology processing. Final, the Gaussian Mixed Model (GMM) algorithm is adopted to update the background image. Experimental results show that the proposed algorithm can detect human in real time and accurately in the stereo garage. It provides a reliable guarantee for the improved safety monitoring of stereo garage.