This paper reviews the hot research topic of the performance deterioration and preventive maintenance of in-service concrete bridges. As complicated structural systems, concrete bridges have characteristics of multiple causes of structural damage, complex degradation mechanisms of materials, and difficult assessment of the structural performance. Due to the combined action of the environmental and loading effects, the properties of steel reinforcement and concrete materials deteriorate, which leads to a decrease in the load-carrying capacity of the structural components and ultimately affects the structural performance of the whole concrete bridge. This paper discusses the performance deterioration and preventive maintenance of the in-service concrete bridges in many aspects, such as the material degradation mechanism, the simulations of the mechanical performance dete-rioration of materials and structures, the evaluations of service performance, the predictions of remaining service life, and the determination of preventive maintenance strategies. Meanwhile, the advantages and disadvantages of the proposed models and methods are compared and analyzed. Consequently, from different levels of materials, components and structures of the existing concrete bridges, it analyses the degradation characteristics of bridge materials at the meso-scale level, investigates the damage mechanisms and failure process of the bridge components, and further examines the deterioration laws of the mechanical performance of the in-service concrete bridges at macro-scale level. Finally, based on the analysis and review of the existing investigations, it proposes the current issues in the performance deterioration and preventive maintenance of the in-service concrete bridges, provides new frameworks for future research, and offers the scientific basis for the smart operation and maintenance management throughout the whole life cycle of bridges.