The invention provides a performance monitoring method of a network storage system. According to the method, actual file reading and writing are simulated, service conditions of a PCU, service conditions of an internal storage, service conditions of a network and actual io reading and writing speed of the storage system in the process are monitored, and finally the information is presented to a user in a curve graph mode. In the method, the functions of large file establishing, file writing simulation, file reading simulation and curve graph downloading are achieved, and the CUP usage rate, the internal storage usage amount, the network usage rate and a disc reading/writing speed curve graph of the storage system can be displayed. According to practical application, the method provides a new standard for performance evaluation of the storage system, the method is more similar to actual user experience and simple, convenient and practical to operate, a storage designer can find out the bottleneck limiting the performance of the storage system conveniently, and a more comprehensive and more visual storage system performance evaluation method is provided for storage users.