Optical and electrical characterization of high-power green LED on Si (111) substrate fabricated by MOCVD with chip dimension of 400 μm×600 μm is studued. The forward bias of the LED with Ag reflector is about 3.59 V under 20 mA, and the light output power is about 7.3 mW with dominant wavelength of 518 nm. The light output power achieves 28.2 mW under 90 mA, the light output efficiency is 7.5%, and the saturated output current is 600 mA. The light degradation of LED with Ag reflector is smaller than that without Ag reflector after 216 h accelerated aging test under 200 mA. This phenomenon is induced by Ag reflector, which can raise the light extraction efficiency and lower the temperature of the chip itself. This characterization of great light efficiency, light degradation and saturated output current suggests that GaN-based green LED on Si substrate has a promising prospect.