High-energy laser weapon is playing a more and more important role in military application. It's an important component of the NMD plan of USA. High-energy laser weapon represents the developing direction of future weapons. It will change the present status of battle field and the mode of operations completely, and it will also change the formation of future war deeply. The research and development of the laser weapon, and the modern laser weapon's function, characteristics and its present development level are introduced. The difficulties and development prospects of laser weapon's application are also analyzed.