Abstract: Long-span high-speed railway bridges usually adopt arch bridge structures with good stiffness and dynamic performance. However, as the service life of the arch bridge increases and the train operating speed increases continuously, the structural performance degrades seriously and is difficult to meet the requirements of normal operation. To improve mechanical performance of railway arch bridge in service, a structural improvement method was proposed based on the principle of triangular stability and small deformation of the truss structure in this paper. Several V-shaped components between the arch rib and the main beam were added, so that it formed several continuous triangles consisting of the arch and beam sections. Triangle structures effectively restrained the main beam and arch rib. The location of the V-shaped components needs to be comprehensively considered for the uniform constraints on the arch ribs and the main beam and the weak position of the structure. The number of V-shaped components should be as reasonable as possible to achieve a reasonable balance between the stiffness of the structure and the temperature response. The results of finite element analysis show that the proposed method effectively improves the rigidity, dynamic characteristics, fatigue resistance and stability of the original structure by reasonably setting the number of V-shaped components and cross-sectional characteristic parameters, the mechanical performance indexes of the arch bridge can reach the most excellent design effect. The reconstructed arch bridge has reasonable structure and convenient construction, which has great value in popularization and application.