Abstract: The formation principle of zero error on high precision fiber-optic gyro was introduced, and the impact of temperature and magnetic field on the zero error of high precision fiber-optic gyro was analyzed in detail. The simulation results show that the zero-bias peak value drift caused by temperature is 0.06°/h. Finally, the theoretical model and experimental research were carried out under the cross-linking condition of alternating temperature field and radial static magnetic field. The experimental results show that under the action of radial magnetic field and temperature, the maximum drift value of the fiber-optic gyro generated by the cross-linking coupling effect is about 1% order of the sensitivity of the radial magnetic field, which is consistent with the theoretical model.