The distributed polarization coupling data measured by optical coherence domain polarizer in polarization maintaining optical fiber coil (PMFC) of fiber optic gyroscope is analyzed, and a polarization coupling amplitude model of measurement point is established. It is found that the polarization amplitude coupling is modulated by broadband source coherence function, and there exists pseudo polarization coupling measurement data. Based on this, a data processing algorithm for distributed polarization coupling data is proposed and implemented. PMFC is fabricated to conduct distributed polarization coupling tests at different temperatures, and the true coupling position and intensity information are extracted. The estimation model of secondary polarization coupling error of PMFC is established, and the bias drift error of fiber optic gyroscope induced by the distributed polarization coupling in fiber coil at different temperatures is estimated. With a high precision polarization maintaining fiber coil analyzer, the bias drift of fiber coil gyroscope is measured at corresponding temperature experimentally. The estimated results agree with the experimental results well.