The development of type II superlattice dual-band long-/long-wavelength infrared focal plane photodetector is reported. Through the design of energy band structure and molecular beam epitaxial technology， dual-band long-/long-wavelength superlattice epitaxial material with good surface quality has been obtained. The 320×256 dual-band long-/long-wavelength InAs/GaSb superlattice focal plane photodetector with pixel center distance of 30 μm was prepared by breaking through the key technologies of low dark current passivation and low damage dry etching. The detector chip is interconnected with a dual color readout circuit， packaged in a Dewar package， and coupled to a refrigerator to form a detector assembly. The dual-band 50% cut-off wavelengths of the photodetector are 7.7 μm （band 1） and 10.0 μm （band 2）， respectively. The average peak detectivity of band 1 reached 8.21×10¹⁰ cm·W^-1·Hz^1/2， and NETD achieved 28.8 mK. The average peak detectivity of band 2 reached 6.15×10¹⁰ cm·W^-1·Hz^1/2， and the NETD was 37.8 mK. Clear imaging of both colors has been achieved， demonstrating the realization of long-/long-wavelength dual-band photodetection.