It is the closest technology to practice in the quantum communication at present to apply single-photon scheme to implement the quantum key distribution (QKD), and may achieve the absolute security in principle. Because of the limit of the response speed of the present single-photon detector, the code rate is still too low to come into practical use. The paper has put up a new idea to design a quick single-photon detector with a multi-port optic-fiber splitter or an optical switch array and many avalanche photo diodes (APD). All of the ports with APD work on time division and cooperate with the logic discrimination and deciding unit by the clock signal, thus the quick detection can come true to high repetition-rate pulses with a single photon. The multiple of the detection rate is decided by the number of the port. The optoelectronic integration can be adopted for the reliable detector. The applying of this detector will largely raise the code rate of the QKD, and stimulate the commercial use.