Ultra-high Performance Concrete (UHPC) has been used widely in bridge engineering recently, especially in local members. However, its application in main bearing structures is relatively few. The paper introduces the design and construction of the first highway UHPC box girder bridge in China—one overpass bridge on Shici Expressway K34+690. The span of bridge is 4×30m, and cross-section of bridge has 3 single-box girders. This continuous bridge was erected by prefabricated assembly as a simply-supported structure first. The full-scale bending test on one of prefabricated girders was carried out, and the optimization design was studied.