With the presupposition of ecological protection to develop，Beijing has gained some achievements in water quality improvement. However，it is urgent to make a comprehensive assessment of water environment quality under the view of basin，to support some precise suggestions for the government. Hydrological process and the pollutants migration process in the basin is the key to give a comprehensive assessment of the water environment improvement. In the first part，firstly，overlapping the monitoring data of the surface water quality of the Beijing Basin in 2018 and 2019 on the river system net，a water quality thematic map of the spatial-temporal distribution in the basin was obtained. Overall in the basin，the surface water quality in the north of the basin was significantly better than that in the south，and that in the west is better than that in the east. After the surface water flowed through the central urban areas，the water quality deteriorated further. It revealed that central urban areas were still an main source of basin pollution. Secondly，the water quality of the river basin in January 2018 was poor，and it improved in July 2018. However，it began to deteriorate again in November，2018. It continued to deteriorate in January 2019. The river water quality improved in July，2018，and the river water quality continued to improve in November，2018. Thirdly，four rivers flowing out from Beijing boundary were found that the water quality on the outflow section from Beijing boundary in 2019 had a very significant improvement compared with that in 2018. The four rivers had reached water quality target in most months of 2019. In the second part，it demonstrated the reasons why Beijing had achieved periodic results，that were scientific strategies to control the pollution，China’s river and lake management system，engineering measures to carry out and system construction to manage water pollution. In the last part，some suggestions for Beijing’s future water quality management would be explored，including new market access mechanisms，coordinated control，source control，and ecological water replenishment to continue.