The utility model relates to the technical field of insulation boards, and discloses a high flame-retardant insulation board, which comprises a flame-retardant mechanism, an insulation mechanism and an anti-corrosion mechanism, the insulation mechanism is arranged in the flame-retardant mechanism, the anti-corrosion mechanism is arranged in the flame-retardant mechanism, the flame-retardant mechanism comprises an insulation board body, and the insulation board body is arranged in the anti-corrosion mechanism. A first flame-retardant layer is arranged in the insulation board body, a reinforcing layer is fixedly connected to the bottom of the first flame-retardant layer, a second flame-retardant layer is arranged at the lower end of the reinforcing layer, and the first flame-retardant layer and the second flame-retardant layer are made of refractory materials. The flame-retardant effect of the insulation board body is improved through the first flame-retardant layer and the second flame-retardant layer, combustion of the insulation board body caused by too high temperature is reduced, potential safety hazards are reduced, the flame retardance is improved, the interior of the insulation board body is insulated through the first insulation layer and the second insulation layer, and the service life of the insulation board is prolonged. The internal temperature of the insulation board body is kept, and the insulation effect is improved.