Heading information is a very important parameter during the precision airdrop system. Magnetic attitude system uses geomagnetic field to measure the attitude information of the vehicle. It has some merits such as small size, high precision and stable performance. However, it also has the inherent characteristic of sensitive to the external interferences, while the Rate gyroscope of inertial device does not have such shortcoming. Thus we can combine the two types of these sensors to measures the heading information. Simulation results prove that the heading error can be improved greatly as the introduction of external attitude information, which meets the precision airdrop system.