Abstract: By using acrylic acid to modify phenolic epoxy resin, an acid resistant resin matrix formulation for pultrusion insulant rod which was toughened by DDSA was optimized. The curing reaction of the modified epoxy resin system was studied by DSC, TGA and FT-IR. The acid resistance, heat resistance, mechanical and electrical properties of the cured compound epoxy resin (cast) and the glass fiber reinforced epoxy resin matrix pultrusion rod were also studied. Experiments show that the resin matrix was suited for pultrusion, and the properties of the insulant rod are excellent.