Ultra-high performance concrete has the advantages of high strength, light quality and good durability. The new technology of strengthening ordinary concrete beam can give full play to the “efficient” of prestress and “light durability” of UHPC. Through finite element simulation and theoretical analysis of the prestressed UHPC reinforced beams in the literature, the ultimate bearing capacity and the key parameters of the beam (UHPC strength and prestressed strength) are studied. The research results show that the chisel treatment process between UHPC and concrete beam can realize the effective interface bonding and ensure the reinforcement effect; the prestressed UHPC beam can greatly improve the bending bearing capacity and the cracking load, the bending bearing capacity formula of ordinary concrete beam is deduced, which is consistent with the literature and finite element simulation results, proving that the reinforcement method can connect with the existing specification and realize the engineering calculation and operation.