［Objective］ In metro lines utilizing ROC (rigid overhead catenary) for current collection, excessive deflection of busbars is observed under cantilever-type suspension structural condition. Therefore, it is crucial to study the deflection calculation methods and the construction installation schemes for busbars. ［Method］ ROC is modeled as a continuous beam structure, and a formula for calculating busbar mid-span deflection is derived and validated using finite element method. The causes of excessive deflection in operational lines are analyzed in relation to the busbar construction installation methods. To further improve ROC smoothness, factors influencing the busbar mid-span deflection are studied. Through increasing busbar cross-section inertia moment, directions for cross-sectional optimization are proposed. ［Result & Conclusion］ ROC should be treated as a continuous beam structure for mid-span deflection calculation. When using cantilever-type suspension structures in ROC, to ensure that the actual deflection approaches the theoretical value, multi-point supports should be implemented during the busbar installation to maintain a level and deflection-free state. Increasing the busbar cross-section elevation and selecting an appropriate cross-sectional structure can significantly reduce mid-span deflection, thereby further enhancing ROC smoothness.