Anti-islanding　protection　is　a　mandatory　feature　for　grid-connected　photovoltaic　system.　A　new　method　for　islanding　detection　is　proposed,　that　is　the　adaptive　PWM　period　disturbance(APD)　which　combined　with　PLL　(phase　locked　loop)　of　grid-connected　current.　This　method　is　a　uniform　algorithm　with　PLL　which　is　equivalent　to　adaptive　frequency　drift　and　adaptive　phase　shift　simultaneously.　Simulation　programs　for　the　control　schemes　are　run　in　PSIM　software　initially　to　see　the　effect　of　control　method.　Afterwards,　control　board　is　designed　to　control　a　6kW　inverter.　Simulation　and　experimental　results　are　also　provided　to　show　that　the　proposed　method　has　advantages　such　as　fast　response,　no　NDZ　and　slight　impact　on　power　quality.