Abstract: Based on uncertainty of the parameteric information about current velocity,the pollutant comprehensive attenuation coefficient,and so on,an unascertained mathematics model for river water quality simulation and prediction is put forward according to the unascertained mathematics theory.The established model can provide not only the pollutant concentration but also the corresponding reliability,it present more useful and scientific pollutant concentration information for water contamination controll plan and water environmental management.The result shows that it is feasible and reliable to simulate and predict river water quality.