A novel approach based on the equivalent sine testing is proposed to evaluate the tracking performance of a photoelectric theodolite by using a dynamic target. The characteristics of the amplitude and power spectra of the dynamic target and the relative tracking errors are analyzed

and the dynamic target is taken as a harmonic source formed by the finite weighted sums of the base frequency harmonics and the weight sums of high harmonics that is the integral times of base frequency. The angular frequency and amplitude of an equivalent sine signal are designed according to the testing desire

and the amplitude-frequency characteristic function value of tracking error system is tested by using the harmonic signal in the same angular frequency with the equivalent sine signal generated by the dynamic target. The amplitude of equivalent sine and the function value are multiplied to get the maximum tracking error of tracking signal

and then the tracking performance is evaluated by using the proposed method. The tracking performance of a photoelectric theodolite is evaluated by this method. Compared with the maximum tracking error of 4.7' measured by the dynamic target directly

the proposed method can offer the maximum azimuth tracking error of 0.65'

which is far less than the desired maximum tracking error of 4'. The result shows that the method can evaluate the tracking performance of the theodolite exactly and can avoid the possible excessive correction of tracking servo system by using dynamic target directly.