The invention discloses a flame-retardant insulating material, comprising a PTT fiber base layer, an insulating layer and a thermal insulation layer. The insulating layer comprises the following raw materials by weight: 25 to 34 parts of organic silicone resin, 15 to 20 parts of an organosilicon cross-linking agent, 15 to 20 parts of silica, 11 to 16 parts of silicon hydroxide, 10 to 15 parts of magnesium hydroxide, 6 to 8 parts of iron oxide, 5 to 7 parts of barium sulfate, 5 to 6 parts of magnesium silicate, 3 to 4 parts of talcum powder, 3 to 4 parts of a lubricant, 4 to 5 parts of an anti-oxidant, 2 to 3 parts of a compatilizer and 1 to 2 parts of an organosilicon leveling agent, wherein the thermal insulation layer is a glass fiber layer. The flame-retardant insulating material has excellent performance and the characteristics of low smoke, no toxicity, no halogen and flame retardation; meanwhile, the flame-retardant insulating material has high tensile strength and shows excellent anti-electromagnetic interference performance when withstanding external mechanical force; and the flame-retardant insulating material is applicable to insulating layers of a variety of electric wires and cables.