Photoelectric theodolites are important instruments for measuring the attitude of flying targets. We present a method for determining the attitude measurement accuracy of a photoelectric theodolite using a real time kinematic carrier phase difference technology (RTK) positioning unmanned aerial vehicle (UAV). The method uses the line formed between the center point of the UAV RTK antenna and a reference point as the axis of the attitude angle to be measured, calculates the included angle between that axis and the datum plane through the RTK positioning value, and uses the angle as the standard attitude against which the attitude measurement accuracy of the photoelectric theodolite is tested. In this paper, the principle of measuring attitude precision is introduced, the uncertainty in RTK and measuring precision are analyzed, and the rule of equipment distribution is discussed. Theoretical analysis and experimental results show that the proposed method can be used for measurement of the attitude accuracy of photoelectric theodolites.