The　control　strategy　of　three-phase　active　power　filter　is　discussed　base　on　one-cycle　control　technology.　No　matter　how　the　source　voltages　are　balanced　or　unbalanced,　the　control　strategy　of　active　power　filter　can　be　determined　by　calculating　the　unbalanced　parameters　of　the　source　voltages　and　determining　the　duty　ratios　of　switches　in　phase.　With　this　control　strategy,　the　active　power　filter　can　make　the　source　currents　in-phase　with　the　source　voltages　which　can　results　in　unity　power　factor　of　the　system.　Finally　the　simulation　of　the　control　strategy　is　made,　and　the　results　of　simulation　show　that　active　power　filter　with　this　control　strategy　can　effectually　compensate　the　harmonics　and　make　the　losses　of　switches　reduced.　Because　it　does　not　need　harmonics　checking　circuit,　the　control　circuit　is　simple　and　has　capacity　of　fast　following.　©　2011　IEEE.