With the use of hypersonic weapons,defense systems are placing greater demands on long range detection capabilities of LiDAR.Multi pulsed LiDAR is the main means of long range detection at present.Limited by the heat dissipation condition of the laser,the current maximum operating frequency of the multi pulse LiDAR is20 Hz,which cannot meet the short range operating requirements of the defense system.In this paper,combining the respective advantages of multi pulsed and single pulsed ranging technologies of LiDAR,the design idea of "multi pulsed + single pulsed" automatic frequency conversion compound ranging is put forward,and a multi pulsed frequency conversion LiDAR is successfully developed.The experimental data shows that the detection range of this LiDAR is 1.42 times higher than that of the single pulsed ranging system,achieving better test results.At the same time,with automatic frequency control measures,the LiDAR can meet the defense system′s short range requirements of high repetition frequency and high data rate(50 Hz)at short range.The research results of this paper are of high application value for the promotion of multi pulsed LiDAR.