Abstract: Climate and human activities have changed the consistency of river runoff, so the calculation of river ecological flow considering hydrological variation is of practical significance for the protection of river ecosystem. Taking Yanggong River as an example, four time series inspection methods were used to test the abrupt change of runoff series of Sanyi section and Jinhe section from 1959 to 2019. The ecological flows in different periods were calculated by using the monthly minimum ecological runoff method and the monthly frequency annual distribution calculation method, and the improved Tennant method was used to evaluate the runoff. Results showed that the variation years were 1997 and 2011; the minimum and appropriate ecological flow of the two sections were calculated in a natural state, sub-natural state, the present state and the state of not considering hydrological variation. It was found that the ecological flow of the sub-natural state was more favorable to the river ecosystem. The ecosystem of the present state was of certain destruction. The process of ecological runoff without considering variation was close to the natural state. In order to determine the ecological flow scientifically, more consideration should be given to the ecological runoff process in the natural state and the sub-natural state. At last, the work objectives and suggestions for the ecological flow of Yanggong River in 2020~2030 should be put forward.