In the process of loading and deformation, the mechanics charactevistics of structured soils will be changed from natural state to damage state (remolded state) with the damage of structure; the damage variable and its evaluation equation are core to reflect the change. The variable expression is given for structured soils damage from the basic idea that damage is a course of energy dissipation. From the different mechanism of energy dissipation aroused by volumetric strain and shear strain, a basic expression that suits to general strain condition is put forward based on principle of superposition of compatible probability event. Through the analysis of the triaxial compression test, the damage evaluation equation to structured soils is set up, and it is revealed that the damage aroused by volumetric strain and shear strain abides by different evaluation law. Numerical calculation result can reflect the text perfectly, and it indicates that the method can reflect the stress-strain relation of structured soils perfectly.