Micro-pulse laser ranging is a new technique of laser ranging,which can achieve long-distance ranging by detecting the echo signal of a single photon.According to the requirement of long-distance laser ranging for airborne application,we made theoretical study and numerical calculation to laser echo signal and background light,and accomplished the simulation optimization of design parameters.The background light noise is suppressed effectively by using spectral filtering together with spatial filtering,and 100 km remote ranging is achieved.Through light splitting,the dynamic range of distance measurement is improved greatly,and the ranging blind zone is decreased to 500 m.The experimental result verified that micro-pulse laser ranging system can detect the echo signal between 500 m and 100 km effectuality,the detection probability PD is not lower than 96% and false alarm probability PFA is not bigger than 0.3%.