We　present　a　novel　structure　of　multi-quantum　well　infrared　photodetector　(QWIP).　In　the　new　structure　device,　a　p-type　contact　layer　replaced　the　n-type　layer　and　on　the　top　of　the　conventional　structure　of　QWIP,　and　a　small　tunneling　current　replaced　the　large　compensatory　current,　which　made　the　device　with　low　dark　current　and　low　noise　characteristics.　The　experimental　result　of　dark　current　accorded　with　the　calculated　result,　and　the　noise　of　the　new　structure　QWIP　decreased　to　one　third　of　the　conventional　QWIP.