Abstract: The current study is inadequate in the damage assessment indexes of freeway subgrade over old mining goaf.In this paper,damage assessment indexes of freeway subgrade over mining goaf were studied by using theories of mining subsidence,mechanics,mathematical methods and associated road specifications.The results showed that freeway damage and deformation with different shape,different speed and other conditions should be determined by using different assessment criterions.The method in this paper is different from traditional assessment indexes,and it allows a larger tilt deformation and smaller curvature and horizontal deformation.The research results were put into practice and the feasibility of the theory was verified.