Abstract: Aiming at the operating distance of photoelectric theodolite indoor detection, we proposed an indoor model for testing the photoelectric theodolite range index. Starting from 4 boundary points in practical work process of the target tracking, we detected the photoelectric theodolite target contrast index, then estimated the working range by taking into account the weather conditions. The experimental results show that the photoelectric theodolite target contrast range is 5%~13%; On the condition of 45N, July, a no rain and no clouds day, the operating range is 30.105 km, and compared with the actual field flying result the error is about 1 km. This method is suitable for estimating the effect distance when tracking the targets under sky background.