The investigation of low resistance ohmic contact on GaAs/AlGaAs quantum well infrared detector is introduced. Combined with the heat treatment process, through testing the I--V characteristics, experiments are conducted on different combinations of Ni/AuGe/Au metal systems to determine the electrode system suitable for n+GaAs/AlGaAs. The heat treatment conditions after metal deposition are preliminary studied. Under the annealing conditions of 400 ℃, nitrogen atmosphere and 60 s, the transmission line model is used to obtain the specific ohmic contact resistance of 3.07×10-5 Ω·cm2 on n+GaAs(1×1018 cm-3).