To test a aspheric surface with F-Number of 4, a highly precise compensation system which is parallel light compensator system is designed. The design wavelength is 632.8 nm and the design residual is 0.0018 λ . A new method of solving the initial compensator structure which is composed of two lenses is discussed. Partial structure parameters are assumed in reason and the other parameters are calculated when the sum of Seidel coefficients from compensator and aspheric surface is the smallest. With the help of MATLAB, the Gauss image height of aspheric surface at the first surface of the compensator is compared with that of parallel light until the iterative error is less than preinstall. Thus the height of parallel light is fixed. Finally, retry to calculate the final initial compensator structure. Each surface′ s Seidel coefficient from iterative calculation is compared with that from ZEMAX, and the result verifies the reliability of this method.