Guided by the “dual carbon” goals, this paper conducts research on the green transformation paths of railway diesel locomotives. By comprehensively applying literature research, case analysis, and cost-benefit analysis methods, it systematically reviews the current transformation status, deeply analyzes the core challenges in the technical, economic, and policy dimensions, and proposes three transformation paths: technological innovation, power transformation, and industrial collaboration. Through quantitative analysis, the transformation costs and benefits are clarified. The feasibility is verified by the power transformation project of the Dongfeng 4D diesel locomotive in Tangshan Locomotive Depot of Beijing Bureau Group. Finally, suggestions are provided from the policy, technology, and infrastructure levels, offering theoretical and practical references for the low-carbon transformation of the depot and the railway industry.