Quantum well infrared photodetector(QWIP)is an important direction in infrared detector research,for its excellent uniformity and high yield.After solving key technology such as material epitaxy,preparation of device,design of read-out circuit and flip-chip bending,long wavelength 640×512 GaAs/AlGaAs Quantum Well Infrared photodetctor（QWIP）was developed.At 77 K,the average blackbody responsibility Rv is 1.4×107 V/W,and the peak blackbody detectivity Dλ* is 6.2×109 cm Hz1/2W-1.The ratio of dead pixels is 0.87％,and the non-uniformity of responsibility is 5.8%.The infrared image of focal plane array is presented at 77 K.