Since the conventional angle-error detection device is complex, hard-using and inadaptable, a detection system for the angle errors of turntables is designed by using the autocollimation theodolite. Firstly, the three-dimensional reflection model is studied, and the exact expression of the model is derived in detail. Then, based on this, a similar formula is given under certain conditions of engineering. Finally, the evaluation of uncertainty is given through the experiment. The expanded uncertainty is 8.9" which verifies the effectiveness of the detection system.