The invention discloses a dissipation thermal-insulation composite material and a preparation method thereof, relates to the field of light anti-ablation composite materials and aims at solving the technical problem that an existing preparation technology is complex and has high cost. According to the composite material, a carbon material is utilized as a base body, the base body is immersed into a molten impregnant under vacuum high-temperature condition, capillary force of micro holes in the base body is utilized to immerse the impregnant into the base body to form the composite material. The preparation method comprises the steps: 1, preparing the impregnant; 2, processing the base body material; 3, processing a graphite crucible; 4, performing high-temperature impregnation. The prepared light anti-ablation dissipation thermal-insulation composite material disclosed by the invention has simple technology, short period, low manufacturing cost and good ablation resistance; the composite material can be applied to electroprocessing and machining, can be applied to manufacturing a throat lining and a gas rudder of a solid rocket engine jet pipe, also can be applied to manufacturing an end cap, a wing leading edge and a tail vane of a hypersonic aircraft and can be applied to manufacturing members of a turning orifice plate and the like of a guided missle.