According to the principle of the acousto-optic communication with the technique of laser Doppler vibration, a novel and compact circuit of frequency discrimination for laser Doppler vibration signal is proposed. Based on the principle of heterodyne detection, one signal is produced by the local oscillator signal mixing with the detected signal and the other signal is produced by 90° phase-shifted local oscillator signal mixing with the detected signal. These two signals are used to acquire the Doppler shift and the sound source frequency. The measurable vibration frequency range can be up from 300 Hz to 10 kHz with the simulating acoustic sound source, and it can be used for the acousto-optic communication.