The invention provides a method for improving surface hydrophobicity of a contaminated silicon sulfide rubber product. The method includes steps of providing the silicon sulfide rubber product contaminated by dirt; and injecting atmospheric-pressure low-temperature plasma jet on the dirt on the surface of the product for conducting surface treatment. The atmospheric-pressure low-temperature plasma jet acts on the dirt on the surface of the silicon sulfide rubber product and enables hydrophobicity of the surface of the silicon sulfide rubber product to be transferred to the surface of the dirt, so that flashover voltage on the surface of the contaminated silicon sulfide rubber product is kept. The processing efficiency is high. Surface hydrophobicity of contaminated composite insulators, post insulators, insulating bushes and the like can be improved ideally. Therefore, the method for improving surface hydrophobicity of the contaminated silicon sulfide rubber product is suitable for popularization and application.