Various physico���chemical parameters were studied to assess the water quality of Ganga river water at Mirzapur in the year 2017. Subsequently, using this physico���chemical parameters, water quality index (WQI) was calculated through mathematical calculations. The experimental values of the various parameters were obtained by adopting standard procedures. These experimental values obtained were compared with the standard values suggested by International bodies such as WHO and ISI. The values were then substituted in the mathematical expression to calculate the WQI. Water Quality Indexing is a simple and convenient method to express the quality of water which leads to a single numeric value through which it could be easily suggested that whether the water is fit for human consumption. In the present investigation, we concluded that the water quality of analysis sites under study very poor water quality during all season.