Abstract: A damage detection method for truss structures based onan improved residual force vector method is proposed. The stiffnessconnectivity matrix of the truss structures is obtained by the sensitivityanalysis, and the stiffness matrix perturbation of the damaged structure canbe expanded to a diagonal matrix by the stiffness connectivity matrix,then with itssubstitution into the residual force vector equation, a new residualforce vector equation expressed by the stiffness connectivity matrix isobtained, which can be solved directly, so the stiffness perturbation of trussbars is obtained, therefore, the damaged bars and the damage extents canbe detected. Becausethe complete modal shapes are difficult to get by measurement, the completemodal shapes are obtained by modal expansion. At last, a numerical example of atruss structure is given, the effectiveness of the proposed method isverified.