Abstract: To reproduce the supreme diameter and high precision grating, the mechanical properties of bearing board in exposure equipment for reproducing grating was analyzed. By summing up the mechanical analysis on bearing board into a flexibility problem, the formula of the relationship between flexibility and thickness was deduced by theoretical calculation. On the basis of the formula, an exposure equipment with bearing board in thickness of 40 mm and diameter of 1 000 mm was used to reproduce a high precision and large diameter thin grating successfully, experimental results show that the biggest diameter error and uniformity error of the grating is 047″ and 8%, respectively, which can meet the requirement for angle measurement system.