The water quality index (WQI) is a tool for determining water quality status and expected to provide a true representation of river quality to the public and decision makers. The Upper Citarum Watershed is one of the largest polluted streams in West Java Province. Therefore, based on the various indices that have been developed in various countries, there is no one specific index that can be applied universally. With the complexity and degradation of water quality in the Upper Citarum River, a Water Quality Index for the Upper Citarum River needs to be developed in order to develop water quality assessment. The main objective of this research is to validate the method for developing a water quality index and to compare between the existing method and developed method, so it is suitable for the Upper Citarum Watershed. The data used includes primary data from interviews and questionnaires with panelists in the water sector, conducted in two stages: the first using the Delphi Method to identify key parameters and the second using AHP to determine parameter weights. Secondary data was sourced from the Environmental Protection Agency of West Java Province and previous studies on the water quality index of the Upper Citarum Watershed. Analysis carried out on the results of interviews and questionnaires found that there were nine parameters and their weights that represented four categories of decline for the Upper Citarum Watershed, namely, TSS (0.07), color (0.038), and pH (0.059) which represented physical characteristic categories; BOD (0.139), COD (0.094), and DO (0.088) which represent a decrease in oxygen and organic levels; nitrate (0.096) and total phosphate (0.105) which represent eutrophication; and fecal coli (0.313) which represent health hazards. Using the Development Method, the Citarum River obtained WQI value ranging from 31.71 to 48.36. Using the Storet method, the WQI ranging between - 50 and - 33. Besides, the value of the Pollution Index method ranges from 8.47 to 13.37. Using IKA Method, WQI value ranges from 8.51 to 13.43. Using the IKA-INA Method, it ranges from 41.71 to 69.98. Using the NSF Method, WQI ranges from 21.49 to 48.44. The status for each water quality method ranges from good, moderate, to poor. The water quality status of the developed method is in accordance with the applicable methods in Indonesia so that the developed method can be carried out for the development of water quality status of other regions also to gain comparison between each water quality assessment method.