The Tian’e Longtan Bridge is a 600 m embedded framework concrete arch bridge with its main span. To achieve the goal of rapid and high-quality construction, this paper briefly compares and analyzes the inner and outer flanges at the joints of embedded framework segments, and, considering the characteristics of the bridge structure, concludes the necessity of a high-level design for the outer flange. In this paper, three external flange structural schemes are proposed, and a three-dimensional elastoplastic model of the bridge is established using ABAQUS to analyze the dynamic characteristics of the flange. Subsequently, the “splicing plate external flange with end plate and positioning hole” scheme is selected based on mechanical performance and constructability. The research content of this paper will have important reference value for the design of other bridge external flanges of the same type.