in this paper, we obtain target information about the distance between laser sources and targets based on the linear frequency modulated laser ranging system. we designed a specific experimental scheme for the ranging of linear frequency modulated semiconductor lasers based on heterodyne ranging experiment. ranging precision can reach micron dimension and range resolution is about 0.002 m within the range of 1-40 m. the ranging method in this paper can apply to laser radars which could be used to capture target information, which is very helpful for tracking, identifying and extracting targets.