Quantitative research was conducted targeting at the impact of precipitation, temperature and land use change on the ecological flow. Using the soil & water assessment tool (SWAT) model and the improved Tennant method, the impacts of precipitation, temperature and land use on the monthly ecological flow process in Yunlong Reservoir basin were quantitatively analyzed. The results show that the area of water and construction land in Yunlong Reservoir basin has expanded significantly during the period of 2008-2018, resulting in the increase of the monthly average ecological flow and the peak ecological flow to a certain extent. According to the calculation results, the growth rate of water area and construction land was 950% and 100% respectively, and the accumulative annual ecological flow increased by 7.82 m3/s. The ecological flow was closely related to precipitation and temperature, which was positively correlated with precipitation and negatively correlated with the air temperature. Compared with the temperature, precipitation had a greater impact on the ecological flow. Under the same amplitude, the increase of precipitation presented a greater impact on ecological flow than the decrease, whereas the drop of temperature gave a larger impact on ecological flow than the rise. It has been calculated that when the precipitation amplitude was +10% and -10%, the corresponding changes of ecological flow was +0.061 7 m3/s and -0.057 0 m3/s, and when the temperature amplitude was +1 ℃ and -1 ℃, the changes of ecological flow was -0.015 1 m3/s and +0.019 3 m3/s, respectively. In conclusion, precipitation, temperature and land use change have a significant influence on the ecological flow.