【Objective】In order to deeply explore the reasonable construction scheme of railway trough beam bridges under complex construction conditions, this paper conducted a systematic study on reconstruction and expansion scheme for such bridges.【Method】Taking the reconstruction and expansion project of a railway trough beam bridge overpassing an expressway as the research object, and facing the complicated construction conditions such as the overlap of the main beam spatial position before and after the reconstruction and the need to maintain traffic, this study conducted a detailed comparative analysis of the structural load-bearing capacity, construction techniques, and traffic diversion for the high-level cast-in-place followed by beam lowering method and the off-site precast incremental launching method.【Result】The research results indicate that the safety factors and stress calculation indicators for the trough beams are all within the acceptable thresholds, meeting the standards. Particularly, the off-site precast incremental launching scheme exhibits higher stress reserves. The high-level cast-in-place followed by beam lowering scheme has a greater beam lowering height and stricter construction requirements, while the off-site precast incremental launching method has lower risks during construction and less impact on the traffic under the bridge. The segmented incremental launching method can effectively solve the problem of jacking difficulty for variable height girders. During the incremental launching process, the side walls of existing frames can be utilized as temporary piers, maximizing the use of existing structures. Both schemes require the implementation of traffic diversion measures during the construction process, but theoretically, there is no need to interrupt the traffic under the bridge.【Conclusion】Both schemes can meet the requirements for maintaining traffic, and the off-site precast incremental launching method demonstrates significant advantages over the high-level cast-in-place followed by beam lowering method in terms of stress reserves, safety factors, and construction risks.