Single-phase　three-leg　Unified　Power　Quality　Conditioner　(UPQC)　is　relatively　a　good　choice　for　power　quality　compensation　in　low-power　applications　as　it　can　achieve　high　performance　with　low　cost.　In　this　paper,　a　decoupling　control　method　is　proposed　to　eliminate　the　interaction　between　the　series　and　shunt　converters　of　the　three-leg　UPQC.　In　the　proposed　method,　output　voltage　of　the　common　leg　is　controlled　proportional　to　the　grid　voltage　and　the　proportional　coefficient　is　optimized　to　ensure　the　compensation　of　both　the　series　and　shunt　converter　with　lower　DC-link　voltage.　Additionally,　theoretical　analysis　and　certain　design　criterions　are　provided　in　the　paper.　Simulation　and　experimental　results　are　also　presented　to　verify　the　feasibility　and　effectiveness　of　the　proposed　decoupling　control　method.