Abstract: A laser alignment measurement method based on a focusing objective and PSD is proposed in order to solve the problem of mathematical model in traditional laser alignment method, which is complex and difficult to work out. Misalignment angle deviation and position deviation are acquired using relations between field of view and focal length of the optical system, and the principle of similar triangle. The measurement principle is simple and easy solving. The experiment results show that when position measurement range is 0.5 mm~1.5 mm and angle measurement range is 0.047 7°~0.143 2°, accuracy of position deviation measurement and angle deviation measurement are 0.035 mm~0.207 mm and 0.000 2°~0.012 8° respectively. Finally, error of accuracy is analyzed and a method considered for eliminating influence of installation error is proposed, and a theoretical formula is given.