In order to guide the processing for grinding to polishing large aperture aspheric mirrors, Ronchi testing system is designed. Firstly, the null compensator is used to replace the compensation grating, which not only for detection of rough machining process by Ronchi test, but also for the testing of interferometer. Secondly, the relationship between the fringe shape and tested surface aberration in the Ronchi system is simulated, and polish process is guided by judging the fringe shape. Then, for a 600mm diameter hyperboloid mirror, Ronchi grating test system, null compensation system and imaging system are designed. The influence of residual reflection of components in test system is analyzed, and the resolution methods are proposed. The result shows that in the Ronchi test system, 5% residual reflection on the plitting prisms surface relative to 0.1%, the illumination of the dark stripes on the image plane increases more than 30 times, and the contrast of the brightness and shade stripes decreases, which is difficult for resolution. When the residual reflection of the grating is greater than 3%, there are bright spots in the center of the stripe, and illumination of the bright spots is 5 times more that of the stripe. By optimizing the structure of the system, the residual reflection on the surface of the component is reduced, and contrast of the image stripes are improved. Ronchi test system was used to detect the polishing process of hyperboloid mirror, and the RMS value after rough polishing of hyperboloid was measured to be 0.042λ, PV is 0.291λ. It can guide process of fine grinding and polishing of aspheric surfaces effectively.