Antenna measurement is very important for the performance verification of antenna radiation. However, when the antenna size is relatively large or the test frequency is relatively low, the traditional measurement method cannot meet the test requirement. In this paper, one kind of antenna measurement method based on the micro UAV is investigated for testing the large antenna in the outdoor environment. The gain pattern of measured antenna is obtained according to the measurement channel model. In this method, the realtime differential GPS is used as the navigation signal, and the geometric control method is combined to control the exact flight trajectory of UAV more accurately. Compared with the traditional navigation method based on GPS, the flight trajectory deviation of UAV is less than 01 meter. Experimental results show that the method can measure the antenna pattern precisely. The gain measurement error is less than 1 dB, which has high engineering application value.