Abstract: Based on the deflection control of concrete beam, smart prestress in beams is introduced to change the value of prestress in beams under different live loads. That is to say, according to the live load on a beam, the deflection of smart prestressed beam can be controlled in the design range if the beam is collocated with a suitable smart anchor, which can change the value of prestress in the smart beam by means of propping up or drawing back the smart anchor. The deflection of an unbonded smart prestressed simply supported beam, which regards midspan deflection as its control target, is analyzed to deduce the control differential equation of structure under moving load. A numerical example is adopted to show the whole functioning process of prestress in the smart beam and explain the feasibility of smart prestress control theory.