Aiming at the detection of the micro-Doppler effect at far distance,the signal to noise ratio (SNR) mathematical models of balanced heterodyne detection for coherent lidar were established. Based on this model,the SNR of balanced and common heterodyne were compared,and balanced heterodyne has obvious advantages on improving SNR under suitable detector′s parameters. By means of experimental verifying and analyzing,the echo signal is more readable after time-frequency analysis compared with common coherent detection,which decreases the error in feature extraction. This research presents an effective receiving method for practical micro-motion remote sensing.