To reduce the cost of the monitoring system and improve the accuracy of bridge damage identification， this paper used limited sensors to obtain high-resolution modal shapes. Considering the road roughness， the damage identification method is proposed based on the flexibility change rate. In different road roughness levels， the proper orthogonal decomposition is used to analyze the displacement response measured on the bridge under moving vehicle loads to obtain the principal component matrix. High-resolution modal shapes can be obtained by filtering the high-frequency dynamic component information in the principal component matrix. The flexibility change rate is calculated using high-resolution modal shapes by limited sensors as an indicator for bridge damage localization. To verify the effectiveness of this method， simulation and experiments were conducted on a simply supported beam. The results show that this method can accurately detect damage by obtaining the flexibility change rate of high-resolution modal shapes based on limited sensors considering different road roughness levels.