It is difficult to theoretically calculate the laser scattering echo energy from rough surface of whole dimension target for complex environment in actual application. In this paper,the theory of random discrete particle light scattering and random rough surface light scattering are combined. Computer graphics is utilized to exactly build the geometrical model of complex targets. Based on the rough surface characteristic of complex targets, and considering the effect of sand, dust, mist and so on,the change of the laser scattering echo energy from rough surface about whole dimension target with different observation angles and visibility is computed and analyzed. The result can meet engineering precision requirement and can be used for the target optical signature extraction, recognition and classification.