Large-span girders serve as crucial components of contemporary infrastructure. For the design and analysis of these structures, a thorough comprehension of their structural behavior, particularly in terms of flexural response, is necessary. With its superior mechanical characteristics and greater durability, Ultra-High Performance Fiber Reinforced Concrete (UHPFRC) has significantly changed the construction business in recentyears. Due to their potential for achieving longer spans, reduced construction time, and enhanced loading capacity, UHPFRC composite box girders have attracted a lot of attention. Comprehensive investigations are required to study the flexural behavior of large-span UHPFRC composite box girders under various loadingconditions in order to ensure their safe and effective use. The study aims to provide an in-depth awareness of the loading capacity, deflection characteristics, and failure mechanisms exhibited by these girders by applyingfinite element analysis (FEA) techniques. The findings of the current investigation might inform the creation of large-span UHPFRC girder designs that are more effective and dependable, promoting sustainable and resilientinfrastructure for the future.