After top layer of 2.5 μm being removed, surface of optical component becomes smooth and flat, and rms roughness is less than 1.45 nm in the range of 0.9 mm×1.2 mm. Content of impurity element (Fe, Ce ect.) is reduced and the size of sub-surface defect is decreased. Periodic polycrystal structure appears at surface of fused silica after being modificated resulting in the increment of transmittance from 400 to 1100 nm, damage is restrained and damage threshold raises. With increasing of modification depth, damage probability of optical component reduces further. Results indicate that reactive plasma modification will be a hopeful method for rapid and nondestructive processing of large surface fused silica optical component.