Abstract: In order to measure the incident angle of light, a new light incident angle measuring system based on conical lens was designed. Using the diaphragm, the conical lens and image receiving device could obtain a complex light spot image. These images were formed by multiple refractions and reflections after the light entered the conical lens through the aperture. The image feature information of the light spot was obtained through image processing, and then the incident angle of light was solved. With this measurement scheme, the angle measurement range can reach to 80°, and the accuracy can reach up to (1×10⁻⁴)″. At the same time, the scheme has a simple structure, small size and does not require cumbersome installation and debugging. Compared with the existing single-spot measurement methods, the conical lens in this solution has an angle magnification effect, which can greatly improve the measurement accuracy and has a large field of view, and the pixel resolution of the image sensor has little effect on the measurement results, and the system luminous flux is large. So it is easy to obtain a higher signal-to-noise ratio.