The joint technology of new and old bridges aims to improve traffic capacity by splicing new bridge sections on the original bridge foundation to form a complete bridge deck, in order to meet the increasing demand for traffic. In response to the shortcomings of traditional splicing technology in construction efficiency and durability, this article systematically explores the complete application of bridge rapid widening technology, including the selection of upper and lower structures, the design of splicing joint structures, and the selection of splicing materials, based on the Jiamin connection line project. In addition, this article analyzes and reflects on the technical difficulties in engineering, and proposes key technical issues in the process of bridge widening, such as the adaptability of structural joints, quality control of joint construction, and foundation settlement issues. It also provides valuable practical experience and theoretical guidance for similar projects.