Based on the actual prestressed UHPC-RC (ultra-high performance concrete-reinforced concrete) composite beam without web reinforcement project, the innovative design scheme of 30-m-span prestressed UHPC-RC box section composite beam without web reinforcement is discussed in depth. Through the comprehensive use of the related standard formulas, the performance of the composite beam under the limit state of structural bearing capacity and the limit state of normal use is comprehensively evaluated. The results show that the key indicators of the composite beam meet the requirements of the current specification and show excellent structural performance. In order to further verify its flexural performance, the flexural test of full-scale model is carried out and preparation process of the test beam is introduced. The crack development pattern and load-deflection curve of composite beams under flexural load are studied. The test data show that the UHPC-RC box section composite beam has excellent performance in flexural bearing capacity. In the process of flexural failure, the cracks develop more and dense, and the deformation is sufficient, showing good ductility characteristics. This study not only provides empirical support for the design and application of prestressed UHPC-RC box-section composite beams without web reinforcement, but also provides valuable reference for future research in related fields.