The invention discloses a cyanobacteria water collecting gate, and relates to the field of water environment treatment, in particular to a cyanobacteria water collecting gate with cyanobacteria waterbody replacement application, a good replacement effect and a stable structure. The cyanobacteria water collecting gate comprises a gate assembly, a gate groove embedded part, pull rods and hydrauliccylinders, wherein the gate assembly is installed on the gate groove embedded part, the number of the hydraulic cylinders is two, the hydraulic cylinders are installed at two ends of the gate groove embedded part respectively, and hydraulic rods which vertically rise and fall are arranged on the hydraulic cylinders; and each pull rod is in a shape of an inverted L, the pull rods are arranged at two ends of the gate assembly, vertical segments of the pull rods are connected with the gate assembly, and horizontal segments of the pull rods are arranged above the hydraulic cylinders, and are connected with the tops of the hydraulic rods. The cyanobacteria water collecting gate is compact in arrangement, and by running the gate, water bodies rich in cyanobacteria and water flows with consistentrunoff are discharged, so that water body replacement is achieved. Not only can as much cyanobacteria as possible be collected, but also waste of excess precious water sources is avoided.