Type II superlattce (T2SL) photodetectors, which is composed of III-V semiconductor materials InAs/GaSb or InAs/Ga1-xInxSb, have experienced significant improvements in both theoretical structure design and experimental device realization in the past few years. The bandgap engineering and band structure engineering provides T2SL with some advantages over mercury cadmium telluride materials, particularly for very narrow band gaps. These inherent properties, such as a higher effective electron mass and large separation of the heavy and light-hole bands to suppress Auger recombination, make them an attractive material for very long wavelength infrared (VLWIR) detectors. By summarizing and analyzing of related papers published in recent years, an overview on issues in the development of T2SL/VLWIR detectors is provided, such as basic concepts, structure, performance optimization, numerical modeling, electronic properties and etc.