In order to solve the problem that the pre-damage parameters of damaged structures are not available in most cases and the higher order modes of structures are difficult to obtain in practice，the damage identification method of generalized uniform load surface is deduced theoretically and proposed. The damage indexes of generalized uniform load surface curvature and the generalized uniform load surface curvature is fitted based on the least square polynomial have been constructed respectively. Taking the T shaped simply supported beam fixed at both ends as an example，the paper analyzed numerically and compared the damage identification effect of four indexes which are flexibility curvature，uniform load surface curvature，generalized uniform load surface curvature and generalized uniform load surface curvature based on least square polynomial respectively. The results show that：all above four indexes only need low order modal parameters to identify the damage，but the latter three indexes are better than the first one；The index of generalized uniform load surface curvature has smaller truncation error than that of uniform load surface curvature，and has certain anti-noise performance；Only the index of generalized uniform load surface curvature based on least square polynomial needs the parameters after structural damage，which has more practical application value.