A method of multi-beam laser heterodyne measurement for magnetostrictive coefficient is proposed. Based on Doppler effect and heterodyne technology, loading the information of parameter under test to the frequency difference of the multi-beam laser heterodyne signal by the frequency modulation of the oscillating mirror, this method can obtain many values of parameter after the multi-beam laser heterodyne signal demodulation simultaneously. Processing these values by weighted-average, it can improve the accuracy of the parameter. The magnetostrictive coefficient of the sample under different carrents is simulated by Matlab. The obtained result shows that the relative error of this method is just 0.48%.