The invention provides a system and method for improving the photon number resolution ability of single photon detectors. The system includes the multiple single photon detectors, a plurality of reading circuit, a plurality of level switching circuit and a combiner, wherein input ends of the reading circuits are correspondingly connected with output ends of all the single photon detectors one by one; input ends of all the level switching circuits are correspondingly connected with output ends of all the reading circuits one by one, and input end of the combiner is connected with output ends ofall the level switching circuits. According to the system for improving the photon number resolution ability of the single photon detectors, when responding photon number is high, peaks of output signals of the reading circuits are distinguished, and thus a high photon number resolution dynamic detection range can be obtained; and the detecting efficiency of the single photon detectors can be guaranteed, meanwhile the signal-to-noise ratio of the single photon detectors is improved, and thus precision of statistic data of the single photon detectors is improved.