In　this　study,　a　novel　nanomaterial　Cu2　O/SiO2　was　synthesized　based　on　nano-SiO2,　and　the　inhibitory　effects　of　different　concentrations　of　Cu2　O/SiO2　on　the　growth　of　Microcystis　aeruginosa　(M.　aeruginosa)　were　studied.　At　the　same　time,　the　mechanism　of　Cu2　O/SiO2　inhibiting　the　growth　of　M.　aeruginosa　was　discussed　from　the　aspects　of　Cu2+　release,　chlorophyll　a　destruction,　oxidative　damage,　total　protein,　and　the　phycobiliprotein　of　algae　cells.　The　results　showed　that　low　doses　of　Cu2　O/SiO2　could　promote　the　growth　of　M.　aeruginosa.　When　the　concentration　of　Cu2　O/SiO2　reached　10　mg/L,　it　exhibited　the　best　inhibitory　effect　on　M.　aeruginosa,　and　the　relative　inhibition　rate　reached　294%　at　120　h.　In　terms　of　the　algae　inhibition　mechanism,　Cu2　O/SiO2　will　release　Cu2+　in　the　solution　and　induce　metal　toxicity　to　algae　cells.　At　the　same　time,　M.　aeruginosa　might　suffer　oxidative　damage　by　the　free　radicals,　such　as　hydroxyl　radicals　released　from　Cu2　O/SiO2,　affecting　the　physiological　characteristics　of　algae　cells.　Moreover,　after　the　addition　of　Cu2　O/SiO2,　a　decrease　in　the　content　of　chlorophyll　a,　total　soluble　protein,　and　phycobiliprotein　was　found,　which　eventually　led　to　the　death　of　M.　aeruginosa.　Therefore,　Cu2　O/SiO2　can　be　used　as　an　algaecide　inhibitor　for　controlling　harmful　cyanobacteria　blooms.　©　2019　by　the　authors.　Licensee　MDPI,　Basel,　Switzerland.