Abstract: Instrumented indentation technique (IIT) is a new technique for measuring the mechanical properties, such as elastic modulus, yield strength, tensile strength and hardness of in-service equipments. By IIT, the load-depth curves could be obtained after the indenter pressing in the material surface, and then each mechanical properties could be gained by analyzing the load-depth curves. By this technique, the mechanical properties of in-service equipments can be detected nondestructively.