本文简述了双光栅形成光拍信号的过程与微弱振动测试的基本原理，通过仿真计算与实验测试相互对比，对光拍信号的表达式进行了修正，振幅修正系数是由于光栅振动带动衍射光斑振动而产生的; 同时，本文通过仿真计算解释了光拍信号毛刺的产生原理，光拍信号的毛刺是由于高级衍射带来的，要想降低毛刺对光拍信号的影响，应尽量使光栅条纹平行或者降低光路中激光强度，以此降低高级衍射对光拍信号的影响.

In this paper，the formation of the optical beat in double grating diffraction and the related principle of weak vibration measurement are presented. By comparing the simulation results with the experimental results，a modification of the optical signal expression is established. It is found that the vibration of the grating induces the vibration of the diffraction spots and causes the modification. In addition，the mechanism of the burr signal caused by the senior diffraction of the grating is revealed and the suppression methods are studied. One of the methods is to make two gratings as parallel as possible，while the other method is to suppress senior diffractions by reducing the intensity of light source properly.