This paper proposes a novel method of multibeam laser heterodyne measurement for an electrostriction coefficient. Based on the Doppler effect and heterodyne technology, loaded with the information of length variation to the frequency difference of the multibeam laser heterodyne signal by the frequency modulation of the oscillating mirror, this method can obtain many values of length variation caused by different voltages after the multibeam laser heterodyne signal demodulation simultaneously. Processing these values by a weighted-average method, it can obtain length variation accurately, and eventually obtain value of electrostriction coefficient of metal by the calculation. This novel method is used to simulate measurement for electrostriction coefficient of PZT under different voltages by MATLAB, and the obtained result shows that the relative measurement error of this method is just 0.98%.