Abstract: Based on the high ratio of live load to dead load, this paper proposes a smart prestressed beam, which can change the value of prestress under different live loads. According to the live load on the beam, the deformation and strain of the smart prestressed beam can be controlled in the design range if the beam is collocated with suitable telescopic mechanisms, which can change the value of prestress in the smart beam by means of propping up or drawing back telescopic mechanisms. The deformation of a steel beam model, which uses analog signals control system and regards mid-span deformation as its control target, is analyzed to show the whole function course of prestress in the beam under three typical locomotive loads. Simultaneously the strain of a cable-stayed bridge model, which uses digital signals control system and regards mid-span strain as its control target, is also introduced. The result of experiments validated the feasibility of smart prestressing control theory.