The principle of optical dualbalanced coherent receive is deduced using Jones matrix, the IQ signal is obtained that contains all the optical information,and the signal processing algorithm based on the IQ signal to demodulate optical signal information is given. Based on this principle, a highspeed MEMS scanning laser heterodyne interferometer is designed, and the thickness map of the test glass is obtained. The interferometer wavefront phase extraction accuracy achieves 0.01 radians, the measurement speed reaches 40 frame/s, and the maximum measured diameter can reach 300 mm, which show the broad application value in realtime optical detection.