Abstract: Piping system is a complex structure with multi-supports, and it is difficult to evaluate the vibration isolation performance of the system with traditional methods. A beam-rectangular-plate model is used to analyze the vibration transmission characteristics of the piping system in this paper. Furthermore, the pipe vibration isolation and its performance evaluation methods are studied with theoretic, numerical and experimental analysis based on vibration power flow theory. The theory analysis shows that the power flow criterion can reveal the information of each mode and dynamic characteristics of the whole system, as well as quantify the vibration isolation efficiency. Such a criterion can be used to estimate the primary and secondary vibration transfer paths and isolation efficiency of the whole system with multi supports.