Doppler frequency extraction algorithm is one of the key technologies of laser Doppler velocity radar. It has a direct effect on the measurement precision,operating range and dynamic response range. Taking a typical laser Doppler velocity radar as an example,the composition and key technologies of the laser Doppler velocity radar system are introduced. Performance indexes and technological parameters of typical laser Doppler velocity radar systems at home and abroad are compared and analyzed. Furthermore,varieties of algorithms which are used to extract Doppler frequency are studied. Also,the merit and demerit of these algorithms are summarized. Finally,the Doppler frequency extraction algorithms are prospected.