The detection performance and false alarm suppression of laser radar with Geiger-mode avalanche photodiode(GM-APD)is investigated.Based on the system working principle and detection time sequence,under the condition that long dead-time and the echo pulse width are larger than the resolving time of the time-to-digital converter(TDC),the theoretical model of the target detection probability and false alarm is established,and the influence of the echo intensity,echo pulse width,noise and echo position on the detection performance is analyzed.According to the detection model of the dual detector structure,the effects of dual detector structure on improving the system detection performance are studied.The results show that,as echo intensity is stronger,echo pulse width is narrower,noise is lower,and echo position is further front,detection performance is better.Using dual detector structure,the false alarm can be well suppressed with AND gate,the target detection probability can be improved with OR gate,and higher target detection probability and lower false alarm can be achieved with AND gate and OR gate.