The invention provides a test system for testing metal frictional damping characteristic in a wet steam environment. The system comprises a wet steam generator, a friction experimental facility and a testing device, wherein the wet steam generator contains a steam boiler, an air storage tank, a pressure regulating valve, a high-pressure water injector, a humidometer and a nozzle; the friction experimental facility contains a vibration exciter, a crossbeam, a friction pairs and a cylinder; the friction pairs contain a first friction block and a second friction block which fit with each other; and the testing device contains a laser vibrometer and a piezoelectric force transducer. By the adoption of the test system for testing metal frictional damping characteristic in a wet steam environment, metal frictional damping characteristic in a wet steam environment can be measured, and the range of the metal friction study is expanded effectively. By the use of measuring results obtained by the test system, accurate data can be provided for design of a turbine blade damping structure in a wet steam environment, and it is of great significance for raising the design level of a turbine blade.