Objective To Study the criteria of assessment on the degree of mental damage due to in-jury. Methods A retrospective study of 297 mental damage cases caused by injury expertised by the depart-ment of legal psychiatry of Tongji Medical College, Huazhong University of Science and Technology from July 1986 to December 2002 was conducted. Results In 297 cases, 91 were heavily injury, 93 were moder-ate. 44 cases were slight injury, and 69 cases between injury and disease. Conclusion The Study proposed a concrete and practical assessment criteria of forensic expertise of mental damage by the analysis of these 297 cases. We hope this criteria is developed into perfection in future forensic expertise.