The laser warning system performs warning positioning by extracting the relevant parameters of incoming laser, and its angle positioning accuracy is directly related to the battlefield survivability. In order to effectively improve the angle positioning accuracy of the laser warning system, an algorithm for high-precision measurement of incoming laser parameters was proposed based on the principle of grating diffraction laser warning. Firstly, the laser warning system was calibrated, and the 0-level spot center of the diffraction spot calibration image was accurately extracted by Gaussian fitting. The laser angle of the future attack was fitted with the spot center of the corresponding angle. According to the fitting results, the angle parameters of the incoming laser corresponding to the diffraction image of the spot at any angle were determined. The experimental results show that the azimuth measurement error is better than 0.29°, and the pitch measurement error is better than 0.38°. The algorithm effectively improves the measurement accuracy of the laser warning system.