The system theory of imaging ranging lidar is researched and the 1064 nm lidar system with photon counting detection is described.The photon counting detection technique and the improvement of the signal-to-noise ratio are analyzed theoretically.The improved signal-to-noise ratio for the weak signal detection with pulse accumulation technique is experimentally proved.The sub-duplicate relationship of photon accumulative pulse and the signal-to-noise ratio is presented experimentally with the different distant targets.In addition, the application of photon counting detection technique to the two difference imaging mode is discussed,The results indicate that the higher detection probability with broad beam emitting and photon counting detection can be obtained than the single-beam scanning mode.[