In deep space laser communication, in order to meet the requirements of long communication distance and high communication rate, the detection system combining PPM and single-photon detector is often used. Starting from the recovery time characteristics of single-photon detectors, this paper derives the detector unit detection probability and false alarm probability models, and establishes a multivariate single-photon detector array BER model based on signal “or” hard judgment and maximum count value judgment. Simulation analysis results show that in the 16-PPM and RS(15,8)coding system, in order to achieve a rate of 1.22 Gbps, the BER is better than 10^-7 communication, when the number of detectors is 4, the detector recovery time should be equalor less than 3.2 ns, when the number of detector units is 25, the detector recovery time should be equalor less than 10 ns.