Circular grating is an important tool to achieve ultra-high precision full circle Angle measurement, which plays an important role in micro and nano machining, aiming and positioning, metrology science and other fields. The circular grating self-calibration technique overcomes the problems of small measuring range and lack of higher reference datums by arranging reading heads and using specific data processing methods to separate systematic errors, thereby enabling self-calibration. To improve the Angle measurement accuracy of circular gratings and reduce the harmonic suppression in circular grating self-calibration, a multi-reading-head self-calibration method is proposed to increase the harmonic residual order. Based on the transfer function method, the relationship between the residual order and the Angle of the reading head is studied, and the formula for calculating the Angle of the multi-reading head with the residual order of 360 integers is established. The calculation results show that for the data sampled from 360 points, the residual of layout 1 in the comparison experiment is 0.8″, and the residual order is an integer multiple of 6. Layout 2 has a residual of 0.2″, and the residual order is an integer multiple of 40. The proposed layout 3 obtained by this method has a residual of 3×10-13″, and the residual order is an integer multiple of 360. By conducting a self-calibration experiment with six reading heads, the proposed method eliminates 94.37% of the errors in the circular grating angle measurement system, achieving full-circle calibration with excellent repeatability. This demonstrates the method′s effectiveness in practical applications. This calibration method significantly enhances the order of harmonic residual in the self-calibration of circular gratings, which offers valuable reference for mitigating harmonic errors in angular measurements and supports the development of ultra-high precision angular displacement sensors.