In order to solve the problem that in the dual axle rotating modulation inertial navigation system the angle between the horizon roller of the system and horizontal plane can't be removed, this paper provides an on-line self calibration method based on inertial navigation system, and this method realized the on-line self calibration of the inertial navigation system by calculating bias and scale factor both of the gyroscope and accelerometer, solving the problem that in the dual axle rotating modulation inertial navigation system the angle between the horizon roller of the system and horizontal plane can't be removed, providing an calculable basis for the prediction of attitude angle and realizing on-line autonomous self-calibration.