Aiming at the problem that nonuniform thickness of sputter deposited film on large-caliber optical components, the ion beam sputtering planarization layer was used to improve the surface roughness of the optical elements. The film thickness of the center and edge of optical elements depositing surface was measured by the film thickness detector, and the dwell time ratio of the center to edge was calculated. The dwell time distribution was fitted by MATLAB, and the value was corrected by the obtained data step by step. The experimental results show that, when the dwell time ratio is revised to -26.6%, uniform film can be achieved on optical elements with a diameter of 300~600 mm. Taking a Si film on the surface of fused silica as an example, the experiment is carried out for 6 h, the film thickness is 212.4±0.3 nm, and the film uniformity can reach up to 0.4%.