In order to obtain real-time flight ammunition's roll angular velocity, angular velocity measurement method was proposed based on geomagnetic components.The method uses a geomagnetic sensor to obtain its projected rate of change in the earth's magnetic field strength tri-axial projectile, combined with rotational movement of rigid model, using the extended Kalman filter to get the roll angular velocity of ammunition.The proposed algorithm is different from other angular rate estimators, it does not use missile attitude, makes the algorithm applicable to rolling ammunition.The simulation results show that:the algorithm can efficiently estimate angular velocity of rolling ammunition, the error is in the allowable range, it has higher application value.