The detection performance of range detection laser radar which uses a single Geiger-mode avalenche photodiode (Gm-APD) with single-pulse is reported. Based on the model of single photon detection with a Gm-APD, research on the detection and false alarm probabilities (PD and PFA) with accumulated single-pulse detection at long dead-time is done. Research on the influence on PD and PFA is done, when the location of target bin in the strobe gate and the mean signal photoelectrons vary. The PD and PFA under different numbers of accumulated detection are compared and analyzed. Theory and numerical results show that accumulated detection can improve the detection performance, and when the accumulated number increases to three times, the detection performance can be very significantly improved; good control of the opening time of the strobe gate can significantly improve the detection performance; when Gm-APD receives a laser pulse, only four photoelectrons can make the detection performance best.