Light is essential for plant growth, affecting plant morphology and physiology. Photovoltaic agriculture (APV) was proposed in the early 80s, but generating electricity on the farm field without influencing the growth of crops has been a challenge for researchers. In this paper, we proposed a newly designed improved photovoltaic agriculture system which can solve this problem optically. Using refraction from groove glass plates, the improved APV system provides crops appropriate light intensity and uniform illumination. We designed the groove glass plate by calculation and simulation. To investigate how different crop grows under different light environments, we examined yield and quality (nutrition) of lettuce under different light conditions. Four different treatments were applied including conventional field environment as the control, conventional APV facility, improved APV system and improved APV system with LED plant fill light lamps. The results indicate that lettuces under the improved APV system had similar yield to the control, and has more than twice the yield of lettuces under the conventional APV facility. In addition, lettuces grown under the improved APV system had a higher nutritional value. These results show that the improved APV system has advantages for wide spread application.