To satisfy high precision testing of interferometer, rotation method to calibrate interferometer’s system error is used for absolute test and improving precision. The method based on properties of Zernike polynomial, which can be realized in two ways: N-position and Two-position method. Theoretical analysis and experiments are taken on both N-position and two-position rotation methods, and results and error analysis are given. The experimental results show that the solutions of the two methods are nearly the same, and the PV value of the difference is 0.006 λ, and RMS is 0.001 λ. Error analysis show that the rotation error of two-position is smaller. So two-position method has higher precision than N-position method.