The functional hierarchy and the performance degradation characteristic of the canned motor pump (CMP) used in nuclear power plants (NPP) are analyzed. And to model the performance degradation of CMP, a hierarchical model based on multi-Agent system (MAS) is proposed. In the model, the framework of the system is designed and the disadvantages of current assessment are conquered. According to the function structure of CMP, the performance degradation and prediction Agents for each hierarchy are divided and the concrete functions for each Agent are also defined. The MAS model provides a guidance template to implement equipment performance degradation and prediction system.