Present study was carried out in river kosi, Rampur district, India to assess the river water pollution for that, six sites are select to collect samples where industrial & domestic waste is regularly mixing in river kosi and by these activities river water become polluted. The samples were analysed to measure the DO, BOD, COD, TS and alkalinity. The collected data were use to statistical analysis and some good correlations (by calculating correlation coefficient r and drawing dotted graph) between parameters are established. The regression equation also established between these parameters to assess the extent of pollution in river kosi. The RPD (Relative percentage difference) value is also calculated and low values of RPD indicate that there is a very small difference between measured and estimated values of parameters. This clearly indicates the validity of regression equation that can used to find the value of one parameter if the value of other is known in same water.