Abstract: This paper presents the design of a three-axis fiber optic gyro combined optical path detection system based on a Super Luminescent Diode (SLD) light source. The system employs synchronized temperature control and constant current drive circuits to ensure normal operation of the SLD across the full temperature range. The power supply section incorporates surge protection to effectively prevent transient impacts caused by switching power supplies or environmental changes, thus protecting the components. The detection system monitors the photodetector's output bias voltage under both light and no-light conditions, while simultaneously calculating the assembled optical path system loss through numerical analysis. This approach determines whether the fiber optic gyro's optical path technical specifications meet the design requirements. Finally, experimental validation demonstrates the effectiveness of the three-axis fiber optic gyro combined optical path detection system in batch production processes. The system improved the accuracy stability of fiber optic gyros to 87% and increased the finished product qualification rate to 96%.