Microcystis　aeruginosa,　the　most　common　toxic　cyanobacterial　bloom,　could　cause　severe　environmental　problem　by　producing　and　releasing　lethal　cyanobacterial　toxins　to　water　body.　This　study　investigated　the　electron　beam　irradiation　for　the　inactivation　of　M.　aeruginosa.　The　treatment　process　was　monitored　via　the　measurement　of　chlorophyll　a　concentration,　optical　density,　photosynthesis,　and　antioxidant　enzymes.　At　low　electron　beam　irradiation　dose　(1.0　kGy),　its　performance　is　not　desirable.　High　dosage　of　electron　beam　irradiation　(2.0-5.0　kGy)　can　dramatically　decrease　chlorophyll　a　concentration,　optical　density,　and　photosynthesis　rate　and　affect　activities　of　antioxidant　enzymes.　The　transmission　electron　microscopy　measurement　indicates　that　electron　beam　irradiation　treatment　cause　significant　damages　on　integrity　and　morphology.　Our　results　demonstrate　that　electron　beam　irradiation　is　a　promising　technique　for　quick　and　efficient　inactivation　of　M.　aeruginosa　in　aqueous　solution.