The invention provides a high-toughness flame-retardant cable for an electric power circuit and a preparation process of the cable. The high-toughness flame-retardant cable is prepared from raw materials of a hydrogenated polystyrene-butadiene block copolymer, polypropylene, maleic anhydride, an MCA (melamine cyanurate) flame retardant, aluminum diethyl phosphinate, montmorillonite, silicone powder, dicumyl peroxide, an antioxidant and the like. The hydrogenated polystyrene-butadiene block copolymer has good mechanical property, weather resistance, heat resistance and compressive deformation resistance, and the dielectric strength reaches 39MV/m; the polypropylene has the characteristics of high strength, large hardness, wear resistance and the like, and has relatively high dielectric coefficient and breakdown voltage; the elastic strength of the composite material obtained by modifying a composite material through the montmorillonite, the silicone powder and the maleic anhydride is increased, the thermal stability is improved, the tensile strength of the composite material is increased to 12.75Mpa, the elongation at break reaches 932.5%, the water resistance is slightly reduced, and the balance torque during melting is reduced; with the addition of the antioxidant, the flame retardancy and thermal stability of the composite material are improved obviously, and the flame resistance of the composite material is increased to 32.