Aiming at the temperature effect of half-wave voltage of Y-waveguide modulator on resonant fiber optic gyroscope (RFOG) based on broad spectrum light source, the effect of temperature-induced half-wave voltage characteristics of Y-waveguide modulator on RFOG was studied. The effect law model of voltage characteristics on scaling factors of RFOG system based on broad spectrum light source was established. The model shows that the temperature-induced half-wave voltage characteristics of Y-waveguide modulator will lead to the change of the scaling factor of RFOG system based on broad spectrum light source. A half-wave voltage measurement system of Y-waveguide modulator used for broad spectrum light source was established, and the measurement accuracy of the system reached 1 mV. The influence of the temperature-induced half-wave voltage characteristics of Y-waveguide in the full temperature range in RFOG system based on broad spectrum light source was tested by experiment. The test results show that the half-wave voltage of Y-waveguide modulator is linearly and negatively correlated with temperature. The temperature-induced half-wave voltage characteristics of the Y-waveguide modulator result in a maximum relative variation error of 1 266.01 ×10^?6 in the scale factor of the RFOG system based on the broad spectrum light source.