Abstract: For the purpose of improving precision and practicability of fiber optic gyroscope(FOG) , a current source and a temperature control circuit were designed for driving the light source of FOG. Considering the characteristics of the FOG, a scheme of controlling the driving current by the feed back light from the coupler and detector of FOG was discussed. The testing results indicated that, in a temperature range of -20℃ to 55℃, the present technology can yield a current precision as high as 0.06%, a temperature control precision of 0.1℃, and a variation of light power less than 0.1%.