In this paper, a semiconductor laser with external optical feedback is entered into chaotic motion by increasing the time of the external optical feedback at first. And then, the sliding mode variable structure control scheme is used to control the chaotic motion of this laser system. The advantage of this method is that the stable output laser can be obtained in a short time and the output power strength of the laser can be adjusted flexibly in accordance with the engineering requirement. Theory analysis and simulation results show that the results of the control have powerful stability and robust .Our research results have many helpful values to improve the speed of stable output, flexible adjustment of laser output power as well as efficiency of energy transformation for real laser system.