Vibration　energy　harvesting　is　an　emerging　technology　for　future　self-powering　devices.　This　paper　presents　an　autonomous　piezoelectric　energy　harvesting　power　management　system.　It　is　based　on　Parallel-SSHI　(synchronized　switch　harvesting　on　inductor)　technique　in　a　0.18-mu　m　CMOS　process.　Comparing　with　the　low　efficiency　of　passive　rectifier,　the　peak　efficiency　can　reach　83%　with　the　design　of　charge　transfer　logic　circuit　in　this　paper.　Through　internal　high-precision　currentreference,　external　load　can　be　changed　to　support　the　needs　of　different　systems.　This　design　can　provide　an　input　power　in　the　range　from　a　few　to　several　hundreds　of　microwatts,　and　the　output　voltage　can　reach　4.5V.