Abstract: In order to study the effectiveness of direct fluorination in improving the DC flashover performance of actual spacers in GIS and to promote its practical applications, 126 kV disc spacers and epoxy samples with the same material as the spacers were fluorinated in laboratory. The fluorination of epoxy samples is to conveniently evaluate the physicochemical characteristics and basic properties of the fluorinated layer of the disc spacer. Infrared analysis and scanning electron microscope observation indicate that surface chemical composition and structure of the disc spacer are substantially changed by the fluorination, and the fluorinated surface layer has a thickness of 0.36 μm. Measurements of surface basic properties show that the fluorination leads to two orders of magnitude increase in surface conductivity of the epoxy sample and spacer and obviously accelerates its surface charge decay. The fluorination also increases the surface hydrophilicity and polarity of the spacer. DC flashover tests in 0.2 MPa SF₆ gas reveal that the fluorination increases the DC flashover voltage of the disc spacer by 15.5%, and also obviously enhance the arc resistance of the spacer. The improvement of the DC flashover performance is mainly due to the suppression of surface charge accumulation by the fluorination, and the enhancement of the arc resistance is mainly attributed to the formation of C—F bonds in the surface layer.