Phacoemulsification　is　an　important　surgical　treatment　for　cataracts.　The　location　of　the　surgical　incision　affects　the　surgically　induced　astigmatism,　and　the　typical　surgical　incision　for　phacoemulsification　is　located　on　the　steepest　meridian　direction　of　the　limbus.　The　real-time　location　of　the　surgical　incision　during　the　cataract　phacoemulsification　can　reduce　doctors＇　workloads　and　the　potential　for　human　error.　A　real-time　surgical　incision　location　algorithm　in　microscopic　images　is　proposed　in　this　paper.　It　is　a　two-part　algorithm　that　consists　of　an　iris　external　boundary　detection　algorithm　and　a　rotation　angle　calculation　algorithm.　The　steps　in　the　iris　external　boundary　detection　algorithm　include　image　space　conversion,　image　segmentation,　filtering,　and　least　square　based　circle　detection.　The　eye　rotation　angle　calculation　algorithm　utilizes　the　SURF　algorithm.　Experiments　on　six　phacoemulsification　videos　show　that　the　algorithm　can　locate　surgical　incisions　in　microscopic　videos　accurately　and　quickly.　The　distance　error　of　the　iris　external　boundary　algorithm　is　2.45　+/-　0.136,　and　the　area　error　is　2.69　+/-　0.184.　The　average　running　time　of　this　algorithm　for　one　image　is　65.1　+/-　4.80　ms;　a　demonstration　video,　the　S1　Video,　is　available.　The　algorithm　proposed　in　this　paper　can　determine　the　surgical　incision　location　in　cataract　phacoemulsification　in　real-time　based　on　a　personal　computer　and　can　provide　assistance　for　ophthalmology　surgeons.