The single photon detector is a widely used instrument in the fields of quantum optics, bio-optics, laser ranging and other scientific research. In recent years, with the development of quantum cryptography, single photon detectors have become the single-photon level weak signal detection instrument and become the core equipment for quantum signal photoelectric conversion. WT-SPD series infrared single photon detector is a photoelectric instrument generated on the basis of quantum cryptography communication system research which is inexpensive, low and dark count rated, high stable. Except adopting the gating technology, dead time restraining and a series of other international universal noise reduction and post pulse suppression technology, it increases the original new differential filtering scheme. The instrument use InGaAs avalanche diode as photosensitive element, further reduces the dark count rate when maintaining the high detection efficiency at the same time.