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The optical properties of polymethyl methacrylate (PMMA) with varying degrees of artificial scratches have been studied with the aim of reproducing the change of visibility of an aircraft's PMMA optical windows after being damaged in their service environment.A novel maintenance method that can perfectly restore the optical property of PMMA has been identified and employed in the repair of the scratches that are formed on the surface of PMMA.This convenient and low-cost method entails polishing PMMA with different types of sandpaper to remove the scratches,and then spin-coating the repair solution in order to restore the optical properties of PMMA.The effect of this repair mechanism and parameters of the repair process were studied.The results indicated that the optical performance of PMMA is closely related to the mesh size of sandpaper,and improper parameter selection destroys the general effect of the repair.When the number of sandpaper mesh is low,the size of the abrasive particle is relatively larger,which can cause deeper friction marks on the surface of PMMA optical windows.Surface treatment using 5000 mesh sandpaper lowers surface roughness (Ra=0.566 nm),and optical transmittance in visible range can be restored to more than 88％.