To solve the problem of the restricted accuracy of the polarization maintaining fiber optic gyroscope (PM-FOG), whose static parameters are influenced by its optical path polarization crosstalk errors, from the view of practical applications, the mechanism of polarization crosstalk errors in light path caused by unsatisfactory optical devices and fused points′ axis angle errors is studied. Based on the Jones matrix and correlation matrix, the PM fiber′s birefringence variable which varies with temperature change is introduced, the optical transmission model of PM-FOG in variable temperature fields is built, and the effect of polarization crosstalk errors on PM-FOG zero drift and random walk in variable temperature fields is analyzed and estimated. Meanwhile, the related experiments are carried out to study the effect of fiber coils polarization crosstalk on its static parameters in variable temperature fields. The experimental results and analysis results of model are in agreement, which shows that the model is reasonable.