The invention provides a thermal insulation material and a preparation method thereof, and relates to the field of building materials. The thermal insulation material includes the following raw materials in parts by weight: granite powder, aluminum silicate powder, rock wool, ceramic fiber, quartz sand, crushed stone, cement, bentonite, Glass beads, aerogel, expanded perlite, nano-silicon carbide, magnesia, vermiculite, retarder, air-entraining agent, swelling agent, water reducing agent and water; the preparation method comprises the following steps: (1) weighing Raw materials, (2) roasting, (3) stirring, (4) pressing, drying, cooling and preservation. The invention solves the problem that the existing building material market lacks the thermal insulation material with the characteristics of high compressive strength, good thermal insulation effect and good fireproof effect.