Double-deck arch bridges are increasingly used to accommodate rising traffic volumes due to their excellent mechanical properties, ease of construction, and economic benefits. However, research on double-deck steel truss arch bridges is insufficient, particularly regarding the influence of various design parameters on structural performance. This study focuses on a large-span double-deck steel truss arch bridge as the research object. First, the cable force distributions and the effectiveness of the completed bridge state obtained from four different cable force optimization methods, analyzing the differences between these methods and identifying the most suitable approach for achieving an optimal bridge completed state. Next, it further studies the effects on the structure caused by changes in parameters such as the ratio of side span to mid-span, the height of the main beam truss, and the height of the main arch truss, and deeply discusses the mechanical mechanisms. Finally, it summarizes the patterns observed, providing a reference for the design of similar engineering projects.