The invention discloses a blue green algae growth inhibitor which comprises the following components by weight: 10%-25% of plant extract, 1.5%-5% of a blue green algae complexing agent, 1.5%-3% of blue green algae growth inhibin, 20%-35% of a synergist, 1%-10% of rare earth, 30%-40% of diatom forming soil, 2.5%-8.7% of a bio-enzyme microbial inoculums and 0.5%-10% of humic acid powder. The blue green algae growth inhibitor can be used for killing blue green algae in a long time, and can deprive compulsively blue green algae cell thylakoid pseudo telescopic function for solidifying, sinking, rigidifying and dying of blue green algae cells, eliminating of water bloom and purifying of water quality. The blue green algae growth inhibitor can effectively kill spirogyra, hydrodictyon, chaetophora and bottleneck algae and other mud moss filamentous capsules in an aquaculture pond, and can eliminate a large number of algae attached to meshes in cage culture, and after biological algae removal, beneficial algae and beneficial microorganisms are recultivated to add nutrition balance elements for reactivating the water quality.