Interferometer fiber optic gyros (I-FOGs) have already developed application in various field. TO have higher resolution, however, it is still required to reduce noices. Fluctuation of temperature distribution in sensing fiber coil is one of the dominant noise factor in FOGs. A countermeasure against the drift is specisl coil winding. To get superior performance, however, gyro output compensation with monitored temperature is still needed. In resonatoir FOG (R-FOG), on the other hand, the sensing fiber coil is very short. Then, it is expected that the drift can be reduced. In this paper, we derive an equation describing the drift due to the time variant temperature distribution for R-Fog. By using the equation we calculated the drift both in I-FOG and R-FOG, and compare them. It is shown that the drift in R-fog become much smaller than I-FOG when adopting a special coil winding.