Accumulated surface charges on epoxy insulator under long-term DC operation reduce the flashover voltage and is a serious threat to the safety and reliability of a power system. This study aims to enhance the DC flashover characteristics of the epoxy insulator after treating its surface with graded surface roughness.  Epoxy sample are prepared and graded surface roughness is carried out on cured samples using sandpapers of different gradings. Atomic force microscopy (AFM), water contact angle measurement using a goniometer (JC2000), surface conductivity, surface potential decay, and surface flashover tests are carried out to analyze the significant changes in epoxy resin after graded surface treatment.  The surface conductivity of treated samples with graded surface roughness increases, which will reduce the surface charge accumulation and hinder the flashover. A higher surface roughness at the triple junction will reduce the emission of primary electrons. From a macroscopic point of view, the surface of the sample is polished, and uneven grooves or small pits appear on the surface of the sample which will increase the creepage distance. Thus, the treated epoxy insulator can be used as future dielectrics with improved insulation properties.