Epitaxial films of GaAs/AlGaAs multi-quantum wells were lifted-off from its grown substrate and transferred to a Si substrate,a typical infrared optical window material.The lifted-off sample was fabricated into quantum well infrared photodetector(QWIP).The responsivity and photocurrent spectrum of the lifted-off QWIP is shown in similar to that of QWIP processed from the as-grown wafer.It demonstrates that the lift-off process can be used in QWIP process without device performance degradation.The lifted-off process can provide a new possibility to integrate the QWIP devices with other optical device to enhance the detector performance.