Lidar or laser radar, a modern active remote sensing technique of atmosphere, has been fast developed and widely applied in survey of the atmospheric and the marine environment because of its high accuracy and high time-space resolution of measurement. This paper firstly describes the basic measurement principle of the lidar and then discusses/analyzes the key technologies/methods, and application prospect of the several kind of existing lidar particularly, such as atmospheric environment monitor lidar, the meteorological observation lidar and space borne lidar. Finally, the newest lidar technology and its advances in the domestic and foreign are summarized.