A novel low dark count rate single-photon avalanche diode (SPAD) device was designed and fabricated with the 0.18 μm CMOS Image Sensor (CIS) technology in this paper. The device is comprised of an effective P+/LNW (light N-well doping) junction for photon detecting and a low concentration N-type diffusing circular guard-ring formed by the deep N-well diffusion. The latter prevents premature edge breakdown (PEB) of the junction and ensures it to operate in Geiger mode. The measured results show that the SPAD achieves a low dark count rate (DCR), and the DCR is 260 Hz at an excess bias voltage of 2V for 8 μm diameter active area structure at room temperature.