According to the high thickness and low illuminance uniformity of traditional direct-down type LED panel light, a design of direct-down type LED panel light with the curved surface plate was proposed. Some experiments were designed by applying the Taguchi method and simulated via the TracePro software. After that, the ANOVA theory was integrated to evaluate the influence of the control factors on the illumination, so that the control factors can be optimized efficiently, and the simulation results were verified by experiments. The results show that the arrangement of LEDs has most influence on the uniformity of illumination and the average illumination, which account for 47.4% and 50.2% respectively. When the optimized parameters were set as hexagonal chips arrangement, inclination angle was 30°, there was no microstructure and light mixing distance was 25 mm, the uniformity of illumination on the diffusion plate was 88.3%, which were consistent with the experimental results, and the thickness of panel light was reduced by more than 37.5% compared with the current one. After simulating the illumination of conference room, the results completely conform to the national building lighting standards. This paper provides a theoretical basis to design a direct-down type LED panel light.