In order to improve the accuracy of navigation systems based on microgyroscope, a small gyroscope intergrated system based primary INS has been studied in this work. It has the features of small size and low cost. The transfer alignment is carried out by using the information transmitted from the airborne primary INS. The gyroscope error is estimated by using the information transmitted from the primary INS with the Euler Angle method, which greatly improves the precision of the gyroscope. It was used on the UAV radar system to realize the stability control of UAV radar antenna.