Abstract: The principle and the measurement system of primary calibration of hydrophones in the frequency range 10 kHz to 500 kHz by laser heterodyne interferometry are presented in detail.A stable home-made heterodyne interferometer is established to measure the Doppler shift of a membrane induced by the propagating acoustic field.The acoustic particle velocity is then obtained by zero-crossing demodulation algorithm,and hence the acoustic pressure is reproduced accurately.Hydrophones are subsequently placed at exactly the same point in the acoustic field to be calibrated.Some measurement error sources are analyzed,and a detailed uncertainty budget is given.The expanded uncertainties in the frequency range of interest are shown to be 0.6 dB(k=2).The calibration results of laser heterodyne interferometry are compared to those derived through the free-field reciprocity method,and good agreements are observed.In addition,smaller measurement uncertainties are shown in the laser heterodyne interferometry technique.It is a good preparation to establish the next generation of primary standard and implement the reduction of the traceability chain of underwater acoustic.