According to modulation and transmission characteristics of laser interception, a laser- interception system based on Doppler frequency shift was put forward. The theory of Doppler frequency shift was studied, and the optical coherent balanced detection and quadrature demodulation were discussed. The effects of anti-noise performance and carrier-frequency mismatching on signal recovery were analyzed by numerical simulation and frequency-domain analysis, a technical method for laser coherent balanced interception based on acousto-optic frequency shift was proposed. Experimental results show that noise floor and excess intensity noise can be effectively suppressed by the proposed method, namely signal noise ratio can be improved, and thus non-contact detection for the perturbation at interface generated by acoustic vibration can be realized, which provides an effective technical method for practical application.