The　optimization　of　image　resolution　for　digital　holographic　scanning　imaging　of　biological　cells　is　investigated.　Digital　holographic　scanning　imaging　experiments　on　the　upper　epidermal　cells　of　onions　are　performed　to　demonstrate　the　validity　of　resolution　optimization　algorithm.　In　the　experiments,　the　holograms　of　the　upper　epidermal　cells　of　onion　are　recorded　at　a　certain　scanning　rate,　and　then　are　processed　by　using　the　resolution　optimization　algorithm.　As　a　result,　the　phase　images　of　the　onion　epidermal　cells　with　higher　contrast　and　resolution　are　obtained.　According　to　the　synthetic　holograms,　the　changes　of　cell　nucleus　and　actin　microfilament　inside　onion＇s　epidermal　cells　are　displayed.　In　addition,　the　dehydration　process　and　plasmolysis　phenomenon　inside　onion　epidermal　cells　are　also　exhibited　by　recording　long-term　scanning　holograms　of　living　epidermal　cells.　The　experimental　results　demonstrate　that　image　quality　of　living　onion　epidermal　cells　can　be　improved　by　optimizing　the　algorithms.