Abstract: An improvement to the Direct Stiffness Calculation (DSC) method and corresponding new damage index, Stiffness Variation Index (SVI), is proposed in this paper. SVI is a parameter related to modal curvature and bending moment calculated, respectively, by central difference scheme to displacement and integral method to load. The proposed improvement makes the DSC technique applicable to damage detection of practical bending-type structures. Research on the effect of measurement errors was performed through numerical simulation. Moreover, a continuous steel beam was tested to verify the modified DSC technique in the condition of concentrated damages. The limitation of measurement points and number of modes are discussed. The results show that the improved direct stiffness method is feasible and efficient in the damage detection of bending-type structures.