The invention discloses an adaptive alga removing device. The adaptive alga removing device comprises an adaptive water feeding device 1, a self-operated flow regulating valve 2, a guide tube and a alga filtering net, wherein the adaptive water feeding device 1 consists of a water draining hole 3, a water feeding gap 4, a water storage tank 5, a water draining guide groove 6, a balance weight 7 and the like; surface water with abundant algas enters the water storage tank 5 through the water feeding gap 4, and then flows to the self-operated flow regulating valve 2 through the water draining hole 3 via the water draining guide groove 6, so that the quantity of water in the water storage tank 5 is regulated; the surface water is then drained on the alga filtering net at the lower position via a water draining pipe; and the algas on the alga filtering net are removed mechanically or manually or the alga filtering net is replaced. The adaptive alga removing device has the advantages that a physical method is adopted, driving force and energy consumption are not required, the adaptive alga removing device is a carbon-free environment-friendly device which can adaptively ascend or descend along with the height of the water level; and the problem that surfaces of downwind bays have abundant algas is effectively solved by low cost.