Different merits and limitations of multi-type sensors often lead to the requirement of multi-objective functions in the optimal sensor placement (OSP), while conflicted objectives are very common because of the limited number of sensors and the complex nature of the problem. A response covariance-based multi-objective multi-type sensor optimal placement method has thus been developed for structural damage detection. To assess the performance of this method, an experimental investigation was performed in this study on a nine-bay three-dimensional frame structure. The sensor placement method was applied to the finite element model of the frame structure to find the optimal sensor placement configuration. These multi-type sensors were then installed on the frame structure in the laboratory according to the determined optimal sensor numbers and positions. Different damage scenarios were then generated on the frame structure, which covered single and multiple damage cases occurring at different locations with different damage severities. Consequently, a series of experiments were carried out to assess the effectiveness of the OSP for damage detection. Besides, the optimal and non-optimal sensor placements were compared to each other. The experimental results show that the optimal multitype sensor placement determined by the proposed method could provide satisfactory results for structural damage detection and that the optimal sensor placement yielded better damage identification than the non-optimal sensor placement.