Considering the relationship between the water cycle and rainfall runoff in the basin, this paper is to study the Sanggan River ecological base flow and analyze its sufficiency and lack in Sanggan River by means of restoring computation of runoff and the basic ecological flow calculation. Concerning the annual runoff calculation of Luo Zhuang - Guding qiao and Guding qiao - Cetian reservoir in Sanggan River, the term by term restoring method was adopted. In order to obtain natural runoff of the section, the unmeasured water quantity was restored term by term and then added measured runoff to it. The Tennant method was used to calculate the ecological base flow of the Sanggan River and compared with the results of the minimum monthly average flow method. The average calculated value of the Tennant method over the years is between 25% and 50% frequency years, which accords with the actual situation of the river. Through comparison between the water diversion in irrigation area and the measured runoff variation of Sanggan River, it is found that the water diversion has restricted the ecological base of the river channel. It is necessary to improve the ecological base of the water shortage.