In order to design better optical structure of LED panel light and solve the existing direct-down LED panel light′s shortcomings of large thickness and high light source density, this paper puts forward two mixed optical components including vertebral structure and half spherical structure that have both reflection and projectionand are applied to the design of ultra-thin direct-down LED panel light to increase the coupling distance of light to improve the light uniformity. The light uniformity and light efficiency are researched when two optical components with different structure are applied to LED panel light by Tracepro software, and further experiments were carried out by Taguchimethod. The results show that the light uniformity of the lamps with vertebral structure′s components is 95.42% andits energy efficiency is 92.72% while the light uniformity of the lamps with half spherical structure′s components is 97.67% and its energy efficiency is 92.65%, the reason why its light uniformity is higher than vertebral structure′s is that the optical component with vertebral structure results in too concentrated light direction due to the directional reflection of the reflecting surface.