In fiber optic gyroscope using low-polarization and polarization-maintaining hybrid light path, some single mode fiber components and single mode fiber(SMF) are contained. When SMF bends, the transmitted core-guided mode light and whispering gallery(WG) mode light in SMF interfere with each other, and then affect the transmitted light. A model of the influence of SMF bending on FOG scale factor stability was developed and demonstrated. Simulation and experimental results indicate that the SMF bending can lead to the transmitted light mean wavelength drifting and oscillating under temperature ramping, furthermore leads to FOG scale factor instability. The mean wavelength oscillation amplitude depends on the bending radius.