Quantum well FPA with reflection coupling structure is relatively easy to fabricate compared with the grating coupling structure. In order to explore whether the RC structure could replace the GC structure in the small size range, the MEEP, a software which is based on the FDTD, was used to construct the 3 pixels model of GC structure and RC structure GaAs/AlGaAs quantum well infrared FPA. According to the simulation of the internal optical crosstalk problem of the device, it is verified that when approaching the diffraction limit, the anti-crosstalk effect of FPA with RC structure is stronger than that of RC structure when the pixel’s size is between 5~7 μm and 8.5~10 μm, while GC shows better performance while the pixel’s size is between 7~8.5 μm and 10~12 μm, and the anti-crosstalk ability of the two structures shows close performance in the range of 12~15 μm. For the quantum well FPA with 15 μm pixels and RC structure, the influence of reflection angle, etch depth and the period of quantum well on its performance of fighting against the crosstalk was explored.