The angle measurement deviation of high accuracy rotary table is sensitive to loading condition. The mechanism of varying load influence on angle measurement deviation was presented and analyzed through numerical simulation. At meantime, a series of calibrations were performed to investigate how much the angle measurement deviation will vary when the operation condition vary in load from 0 kg to 5 kg. A series of angle measurement deviation curves were obtained with cross-measurement method. The amplitudes of deviation curves were compared and the Fourier components of the deviation curves were analyzed. The numerical simulation result was proved. The self-calibration method was used to restrain the additional angle measurement deviation caused by varying load and have obvious effect.