The invention relates to a performance evaluation system for integrity of a zirconium alloy fuel cladding for a nuclear power station under an LOCA (Loss-Of-Coolant Accident) working condition. The performance evaluation system comprises a reaction device, a working gas distribution system, a mixed gas supply device, a steam-gas separator, a hydrogen gas analyzer, a water quenching system, a pressure measuring device and a vacuum system, wherein the reaction device comprises a sample chamber, a heating electrode for heating the cladding, and a temperature measurement device for measuring temperatures of the inner wall and the outer wall of the cladding; the sample chamber comprises a quartz tube, an upper end cover, a lower end cover, a mixed gas feeding pipe and an exhaust pipe; the working gas distribution system comprises a first gas tank for storing helium gas and a second gas tank for storing argon gas. The performance evaluation system provided by the invention can be used for evaluating loss-of-coolant of a reactor; after a safety injection system is started, water is injected into the reactor; after the cladding is quenched, the integrity of the cladding is evaluated; and the amount of hydrogen gas released by the zirconium alloy cladding in a high-temperature steam reaction process can also be measured, and equipment support is provided for out-of-pile performance evaluation in a zirconium alloy research and development process.