When the vessels are sailing for a long time, because of the changes in environmental and other factors, which will cause gyro drift, scale factor and installation errors, gyro online calibration is required. This paper uses high precision attitude information which is provided by CNS, installs gyro online calibration models based on quaternion error, a method of on-line calibration for SINS/CNS based on MPF-KF is presented. The results of simulation show that this method is good for online calibration, not only meets the requirements of calibration acuracy, but also reduces the amount of calculation, improves the numerical stability.