Two-stage desuperheater protection system for ultra-supercritical boiler reheater

The invention relates to a desuperheater for a boiler reheater, in particular to a two-stage desuperheater protection system for an ultra-supercritical boiler reheater. In order to solve the problem that an existing large-scale boiler reheater two-stage desuperheater is lack of invalidation protection, and consequently thermal fatigue failures are prone to occurrence, the two-stage desuperheater protection system for the ultra-supercritical boiler reheater comprises a desuperheating water pipe and a two-stage desuperheater, wherein the desuperheating water pipe is connected to an inlet pipe ofthe two-stage desuperheater; and the two-stage desuperheater protection system is characterized in that the desuperheating water pipe is connected to the inlet pipe of the two-stage desuperheater anda desuperheating steam pipe through a tee joint, the far end of the desuperheating steam pipe is connected to a steam source and exhausts steam, the desuperheating steam temperature in the desuperheating steam pipe is between