In　this　paper　an　overall　circuit　of　a　photovoltaic　system　is　designed.　By　analyzing　the　output　characteristic　of　a　solar　cell,　an　improved　MPPT　algorithm　on　the　basis　of　P&O　method　is　put　forward　to　track　the　MPP　of　solar　cell　modules.　The　experimental　results　show　that　the　improved　P&O　MPPT　algorithm　has　higher　efficient　compared　with　the　P&O　method　in　the　same　environment,　and　the　photovoltaic　system　can　keep　working　at　MPP　without　oscillation　and　misjudgment.　So　it　can　not　only　reduce　misjudgment,　but　also　avoid　power　loss　for　constant　perturbation　around　the　MPP.　©　2011　Springer-Verlag.