Abstract: During the construction of the Shibalihe Interchange, the cast-in-place box girder construction needed to cross the existing road, which caused significant disruption to traffic. To address this issue, a door-like scaffold system including steel pipe column and Bailey beam was proposed to ensure the normal traffic flow under the existing road during the cross-line construction. A three-dimensional finite element model was established using Midas Civil to systematically analyze the mechanical behavior of the door-like scaffold system under the combined action of dead load, live load and wind load. Through numerical simulation, the strength, stiffness and stability of the support system were evaluated in detail. The results show that under the action of the upper load, the strength, stiffness and stability of the portal frame support fully meet the design and construction requirements of the cast-in-place box girder. This paper combines numerical simulation with engineering practice to verify the engineering applicability of the support system and provide a reference for the design of similar cross-line construction supports. At the same time, this study further expands the auxiliary decision-making value of finite element analysis technology in bridge construction.