This article is a study of superconducting niobium(Nb)nanowires used as optical and near-infrared single photon detectors.In this paper,the fabrication process of Nb+Al based superconducting nanowire single photon detectors(SNSPD)using lift-off process will be presented.Transition temperature(Tc)of devices is measured with PPMS and good devices are chosen.With a DC bias current applied close to the critical current(Ic),the nanowire showed an electrical signal when illuminated by a laser pulse at the telecommunications wavelength(1550nm).The detection efficiency of 5nm-thickness SNSPD are measured.