Abstract: a multi-step decision method for structural damage detection based on frequency response curvature using a few sensors is presented to improve detection accuracy and reliability. Numerical example of multi-damaged simply-supported beam is used to illustrate the validity of the presented method. The efficiencies and antinoise abilities of three improved methods (improved modal curvature method, improved flexibility curvature method and the proposed method) are analyzed and compared in detail. Finally experimental examples of a multi-damaged pipeline with local reduction and a single-damaged pipeline with local crack based on experimental model are preformed to verify the correctness and feasibility of the proposed method. The results show that the proposed method worked well for the damage detection and the assessments are in good agreement with the actual condition, which is meaningful in the application to damage detection in engineering structure.