Abstract: Two GaAs/AlxGa1-xAs infrared quantum well materials with different structure parameters have been made by using metal organic chemical vapor deposition. The photoresponse spectra are obtained at 77 K by use of Fourier transform spectrometer for two sample-devices of GaAs/AlxGa1-xAs quantum well infrared photodetectors with an Al content of 0.20 and 0.30 respectively. The results show the peak wavelengths of 1# and 2# are 8.38 m and 7.59 m, while they are 9.694 m and 8.134 m according to the Schrdinger equation, and the errors between them are 13.6%, 6.68%, respectively. The crystal structure is investigated by using high-resolution scanning transmission electron microscope to analyse the main reason of the large errors and peak wavelength redshift, which shows that there is thread dislocation and nonuniformity in different degrees. The main reason causing 1# error much larger is the crystal lattice mismatch between AlGaAs and GaAs. The fact that the peak wavelength increases with Al content reducing shows reducing Al content will lead to narrowing of the spacing between subbands and peak wavelength redshift.