Abstract: The explicit and implicit calibration approaches for spacecraft gyros were introduced.The dynamic equation and measurement equation of explicit and implicit approaches were set up,and estimation of calibration parameters was obtained by extended Kalman filter.In particular,the two approaches applied to in-flight spacecraft gyro calibration were compared.The result simulation shows that the performances of the two approaches are basically comparable,and relative accuracy is less than 10%.Sensitivity tests indicate that the explicit filter results are essentially insensitive to variations in given spacecraft dynamics model parameters,but explicit filter implements were easily.