Optic　disc　(OD)　is　one　of　the　most　important　structures　in　retina.　The　automatic　detection　of　OD　is　essential　to　make　Diabetic　retinopathy　examination　more　effective.　In　this　paper,　a　fast　optic　disc　localization　algorithm　is　described.　Our　approach　begins　with　pre-processing,　and　then　the　main　vessels　in　fundus　images　are　extracted　based　on　morphology　methods.　In　the　next　step,　parabolic　fitting　algorithm　by　the　least　square　method　is　applied　to　express　the　main　vessels.　Finally,　we　judge　the　fitting　result　and　defined　the　apex　as　the　OD　center.　The　proposed　method　was　evaluated　in　3　public　datasets.　An　average　accuracy　of　99.05%　at　the　average　time　of　1.08　second　was　achieved.　©　2018　Association　for　Computing　Machinery.