Based on the Jones matrix, the optical transmission model of dual depolarized fiber optical gyros (DFOGs) is built and the theoretical expression of polarization crosstalk error is derived. The effect of the polarization crosstalk error caused by the 45° angle error of depolarizer, the power coupling of polarization crosstalk point, the limited Y waveguide chip extinction ratio and the angle of polarization rotation of the fiber coil on DFOG are simulated and analyzed. Experiments demonstrate the effect of 45° angle relative error between two depolarizers and temperature on DFOG zero drift. Results show that the greater the 45° angle relative error between two depolarizers changes and the higher temperature gradient is, the greater influence on the precision of DFOG will become.