The invention discloses an ecological basic flow system guaranteed through reasonable water storage in a river. The ecological basic flow system comprises a hydraulic dam, an oxygen-pushing microflow aeration device, an aeration pipe and a riverbed, wherein the hydraulic dam is located on the riverbed; the oxygen-pushing microflow aeration device is located below the hydraulic dam; one end of the aeration pipe is connected with the oxygen-pushing microflow aeration device while the other end extends to the upper stream of the riverbed; and the hydraulic dam, the oxygen-pushing microflow aeration device and the aeration pipe are arranged on the riverbed at certain intervals. According to the invention, with flowing of current, drop aeration is realized as the current drops into the water from the hydraulic dam; air can be delivered to the upper stream of the riverbed under the action of the oxygen-pushing microflow aeration device, so mixing aeration is realized; thus, the effect of water purification is obtained. The whole system needs no extra energy and realizes river purification via power produced by the flow velocity and gravity of the current.