•Flexural behavior of UHPC wet joint in prefabricated multi-girder bridge.•Eleven full-scale specimens were tested under bending moment.•Cracking resistance and flexural capacity of the specimens were discussed.•Key factors influencing flexural behavior of UHPC wet joint were revealed.•Configuration and flexural capacity were provided for UHPC wet joint. A new type of prefabricated multi-girder bridge with UHPC wet joint was used in an expressway bridge under construction in China, taking advantage of the excellent mechanical property of UHPC. As a kind of accelerated bridge construction (ABC) technology, the bridge decks are prefabricated in the factory with normal concrete and connected by cast in-situ UHPC wet joint. Straight overlapping of the longitudinal reinforcement was designed in this paper to simplify the complex configuration of the wet joint with annularly overlapped reinforcements in engineering practice. Eleven full-scale specimens divided into five groups were manufactured and tested to investigate the flexural behavior of the multi-girder bridge deck with UHPC wet joint. The influence of overlapping form, overlapping length and reinforcement ratio of the longitudinal reinforcement as well as the section form of the wet joint on the flexural behavior of the UHPC wet joint was revealed and discussed systematically, and compared with the integral concrete bridge deck. The crack load, location of the initial crack, nominal cracking stress, and ultimate load bearing capacity of the specimen were observed and discussed in detail. The test results indicate that the straight overlapped reinforcement is capable of providing sufficient anchorage effect between the rebar and UHPC with a minimum overlapping length of 10 times of the diameter of the reinforcement (10 db). It is demonstrated that the adoption of UHPC is beneficial to simplify the complex overlapping of the reinforcement and minish the width of the wet joint. Increasing overlapping length of the reinforcement has marginal influence on the flexural behavior of the bridge deck in case that the minimum overlapping length is satisfied. However, increasing reinforcement ratio and using the diamond-shaped wet joint are helpful to improve the flexural behavior of the bridge deck including crack load, location of the initial crack and ultimate load bearing capacity. The ultimate bending capacity of the bridge deck with UHPC wet joint was analyzed theoretically and the theoretical analysis results agreed well with the test results and failure mode of the specimens. The present research findings are useful to provide comprehensive understanding on flexural performance and design guidance of UHPC wet joint in prefabricated multi-girder bridge.