Auto-focusing　is　one　of　the　key　issues　in　the　non-mydriatic　fundus　camera,　a　fine　and　rough　combined　auto-focusing　method　is　presented　after　analyzing　imaging　principle　of　the　fundus　camera　and　the　retinal　image　characteristics.　Inscribed　square　fixed　focusing　window　selection　method　combined　with　characteristics　of　fundus　image　field　is　presented,　and　Robert　gradient　function　is　used　to　realize　the　rough　focusing.　The　focusing　window　for　fine　focusing　is　selected　through　auto-focusing　window　selection　algorithm　based　on　local　entropy,　and　image　sharpness　evaluation　function　based　on　Zernike　orthogonal　moment　with　9　pixel×9　pixel　mask　is　presented　to　realize　the　fine　focusing.　The　experimental　results　show　that　the　focusing　window　method　based　on　inscribed　square　is　more　stable,　and　proposed　image　sharpness　evaluation　function　for　fine　focusing　has　better　sensitiveness　and　realtime　performance.　©,　2014,　Chinese　Optical　Society.　All　right　reserved.