This study, the EPANET model was used to simulate changes of hydraulic in the system through analysis method of the water supply pipeline, after collecting the data such as the pressure and flow rate with field measurement data in the study site. Acoordingly, this study used the pressure, water level and pipeline network to determine the Hazen-Williams C Value of the pipeline according to characteristics of system for J-City. therefore, C Value with the smallest margin of error was determined and used as the actual measurement value at the non-observation point to determine the C Value. A correlation analysis was conducted to analyze the relationship between the collected C Value and the physical impact factors in the system. therefore, the C Value presented in this study can be used as reference of the pipeline network at the J-city watershed in the future. When C Value estimated, we proposed a method to estimated the C Value more reliably.