Metal-organic　Frameworks　(MOFs)　as　a　new　type　of　nanomaterials　are　extensively　used　in　various　fields　of　environment　pollution　remediation.　However,　the　MOFs　are　rarely　applied　in　the　removal　of　cyanobacterial　blooms,　and　more　fundamental　investigation　is　warrant　for　more　insights　into　mechanisms　for　algae　inhibition.　In　this　study,　Cu-MOF-74　was　synthesized　by　a　simple　hydrothermal　method,　and　its　inhibitory　effect　on　the　growth　of　Microcystis　aeruginosa　was　studied.　Furthermore,　its　mechanisms　were　explored　with　respect　to　metal　ion　release,　agglomeration,　shading　and　algal　cell　membrane　breakage,　production　of　extracellular　hydroxyl　radical　and　intracellular　reactive　oxygen　species.　The　results　showed　that　the　inhibition　rate　of　M.　aeruginosa　was　372%　after　24-h　exposure　when　the　concentration　of　Cu-MOF-74　exceeded　1　mg/L.　However,　the　addition　of　Cu-MOF-74　at　the　concentration　lower　than　0.1　mg/L　promoted　the　algal　growth.　The　inhibition　of　algal　growth　by　Cu-MOF-74　was　basically　attributed　to　the　presence　of　hydroxyl　radical　and　intracellular　reactive　oxygen　species,　with　the　released　Cu2+　and　cell　aggregation　involved　to　some　extent.　Overall,　nanocrystalline　Cu-MOF-74　is　of　great　potential　in　the　control　of　harmful　cyanobacterial　blooms　and　the　inhibition　is　specific　to　the　concentration　of　Cu-MOF-74.