Safeguarding the ecological base flow is the basic requirement of maintaining the ecological health and functions of rivers. Based on the long series runoff data of Qingshizui, Tiantang, Liancheng and Xiangtang stations in the Datong River Basin, the base flow proportion method, Tennant method, the multi-year average of the driest monthly average flow method, 90th percentile method and 7Q10 method were combined to calculate the ecological base flow of the Datong River Basin. Meanwhile, the early warning scheme and flow control indicators were investigated accordingly. The results show that the calculation results of base flow proportion method is more comprehensive and reasonable, and can reflect the ecological base flow of the basin in each interannual period. According to the calculation, the range of ecological base flow in the Datong River Basin is determined to be 11%-35% of the annual average flow, and the ecological base flow of Qingshizui, Tiantang, Liancheng and Xiangtang stations is 5.57-17.73, 8.68-27.61, 9.08-28.88 and 9.39-29.89 m3/s, respectively. Furthermore, the assurance degree of annual base flow obtained from the guarantee degree analysis reaches 90%. Then, according to the determined ecological base flow, the ecological early warning is categorized into three levels of blue warning, orange warning and red warning, based on which the early warning scheme is formulated to improve the reliability and accuracy of flow monitoring and optimize reservoir scheduling in the meantime.