This paper is based on a super long-span extradosed cable-stayed bridge with a main span of 400 m. In view of the technical challenges of high negative bending moment at the quarter point of the bridge and large deformation during the cantilever assembly process in the non-cable area, a systematic solution was proposed in combination with the entire construction process. This paper proposed three schemes: permanent cable over-tensioning, temporary cable setting, and large segment closure. The bending moment ratio (λ_M) and structural deformation were used as quantitative indicators, and a finite element model was established to compare the three schemes. The results show that all three schemes can improve the structural stress and reduce deformation during construction, but each has its own advantages and disadvantages in terms of implementation difficulty, economy, and effect. Based on construction conditions, economic factors, and finite element analysis, a suitable scheme was selected. A combination of over-tensioning and temporary cable setting was adopted for the background project. At the completed stage, the bending moment ratio λ_M is 1.53 (reduced by 2.47 compared to the original scheme); the tangent assembly deformation is 2.276 m (reduced by 1.175 m). In addition, the temporary cable anchorage structure can be used as the cable replacement and tensioning structure during the operation period, achieving good application results and economic benefits.