The article analyses and predicts the hydrodynamic feature of study area on the basis of mike21 numerical model. It is by the two dimensions pollution diffused simulation method based on the hydrodynamic model. And then it predicts the contributed concentration field of the waste water. Based on the NH3-N in discharge of sewage, it contrasts the impact on water quality in the Yangtze River of the pollution in waste water from time and space. In general, with the decreasing of Baosteel project's sewage water efflux, the pollutant has less effect on the water equality of Yangtze River's contributed concentration year by year.