The output performance of semiconductor laser directly determines the measurement accuracy and long-term operation stability of the optical fiber current transformer. Thus in order to improve its measurement accuracy and stability, a high-precision digital driver circuit of semiconductor laser was designed. STM32 microcontroller was used as the main control chip, high-precision current source chip ADN8810 was used to control the driving current precisely. And integrated temperature control chip MAX1978 was adopted to control the working current of semiconductor coolers to realize the precise temperature control. The experimental results prove that the output current stability is 0.028% and the stability of temperature control is 0.18%. The optical power stability reaches 0.06%, and the wavelength stability reaches 0.05pm. The design can meet the output performance requirements of light source of the optical fiber current transformer.