The invention discloses a method for preparing a high-performance silicon carbide coating on the surface of a carbon-carbon composite thermal insulation material, and belongs to the technical field ofthermal insulation materials. The method comprises the following steps that a carbon/carbon composite thermal insulation material initial green body is prepared, rigid carbon felt with certain initial density is customized according to the size of a required product, the rigid carbon felt is machined to achieve the dimensional accuracy according to the designed product structure and size, and thecarbon/carbon composite thermal insulation material initial green body is obtained; the carbon/carbon composite thermal insulation material initial green body is pretreated, and the surface of the carbon/carbon composite thermal insulation material initial green body is subjected to grinding, polishing, ultrasonic cleaning and drying for use; coating slurry brushing is conducted, and ceramizationtreatment is conducted; deposited carbon treatment is conducted; high temperature sintering treatment is conducted. The silicon carbide coating prepared through the method is firmly bonded with a carbon/carbon composite thermal insulation material matrix, and the coating is not cracked, the strength of the surface coating of the carbon/carbon composite thermal insulation material is greatly improved, and the service life is obviously prolonged.