The traditional modal strain energy calculation needs complete modal shape information. However, it is difficult to accurately obtain the freedom of rotation from the mode shape information. In order to solve the problem, modal strain energy damage identification based on strain mode is studied, and the quantitative identification of structural damage is presented. Based on the relationship between strain and displacement, the transformation matrix between displacement mode and strain mode is obtained; the damage identification equations are derived based on the sensitivity analysis, through the substitution of the displacement modes with strain modes. The structural damage is finally identified via solving the equations using a singular value truncation method. Taking a beam structure with two fixed end as an object, the numerical simulation and experimental investigation are conducted. The results show that both the damage location and severity can be effectively identified from the new proposed method in this paper. Compared with the damage identification method based on modal strain energy and modal expansion, this proposed method has better accuracy and performance under noisy data. The research achievement has a potential value on the structural damage identification of engineering structures.