The impedance characteristics of the fiber-optic gyroscope (FOG) source die are non-linear. In order to ensure the stability of the optical wavelength and output optical power, it is necessary to control the die injection current to be constant. In this paper, after analyzing the super luminescent diode (SLD) light source die, the corresponding constant current driving circuit is designed by using LM324 as the core device, and an experimental test is conducted. The experimental results show that the constant current driving circuit can meet the performance requirements of medium and low precision, low power FOG with the change of the constant environmental temperature. The average output voltage at normal temperature is 100.242 mA, and the relative difference is 0.013 7%.