Aiming at the accurate measurement of muzzle disturbance,it is proposed a method of non-contact measurement that can test the muzzle disturbance angle based on the principle of optical lever.According to the vibration law of the small-caliber artillery in firing process,a mathematical model between the muzzle angle and the two-dimension coordinates of Position Sensitive Detector（PSD）is established.A simulation system is built and the rationality and accuracy of the theoretical model of optical lever has been verified.It lays the mathematical foundation for the practical test system and provides reference for the analysis of muzzle disturbance angle test.