Relative attitude estimation with the stereo vision method is an important part of the autonomous navigation system for Unmanned Aerial Vehicles (UAVs).An attitude measurement method for visual navigation of UAVs based on coplanarity constraint is proposed.Stereo vision is built for images taken by a single camera at different time， the attitude measurement model based on coplanarity condition is established in accordance with the geometric constraint relations of imaging lights of the camera to the same target at different time， and the precise relative attitude parameters are calculated out.Experimental results of the real UAV image data show that the proposed method has higher measurement accuracy and stronger anti-noise ability.Without the synchronization problem of photography in UAV attitude measurement with two cameras， it is of greater flexibility and practicality.