Steam turbine thermal insulation device

The invention provides a steam turbine thermal insulation device. The steam turbine thermal insulation device comprises an outer cylinder and an inner cylinder matched with the outer cylinder and further comprises a thermal insulation layer, the thermal insulation layer comprises an outer wall plate and an inner wall plate, the outer wall plate and the inner wall plate are fixedly sealed and mounted in the inner cylinder or the inner wall of the outer cylinder, multiple staggered through holes are formed in the outer wall plate and the inner wall plate, the thermal insulation layer is composed of the outer wall plate and the inner wall plate on the inner and outer layers, a gap B cavity between the dual layers of wall plates effectively obstructs heat radiation of reheating steam of a high-temperature A cavity to a low-temperature C cavity and the outer cylinder, high-pressure cooling gas is input to the C cavity, through circulation of the B cavity, the gas is imported into the A cavity, the gas enters a ste