The development of the large format polarimetric LWIR quantum well infrared FPA. The 20 μm pitch, 640×512 array was divided into 2×2 unit cells. Each pixel in the unit cell was etched a 1D lamellar grating on it, with four different orientations of 0°, 90°, 45° and 135°, to get the polarimetric information of the incidence irradiation. Based on the QWIP FPA key technologies such as quantum well material epitaxy and chip preparation, the single-chip integration with LWIR and the polarization detection function was realized on the QWIP FPA. The 640×512 polarimetric LWIR QWIP FPA assembly with noise equivalent temperature difference (NETD) better than 30 mK was obtained with the integration the FPA chip with the Dewar and the sterling cooler.