The invention discloses an unbonded prestress and steel-concrete composite reinforcement design method for concrete T-shaped beams. The unbonded prestress and steel-concrete composite reinforcement design method includes steps of firstly, determining unbonded prestress and steel plate-concrete composite reinforcement structures for the reinforcement T-shaped beams; secondly, determining structural parameters of the T-shaped beams prior to reinforcement; thirdly, determining structural parameters of the composite reinforcement structures, to be more specific, initializing the parameters, computing the maximum theoretical thicknesses of reinforcement steel plates, determining the thicknesses of the reinforcement steel plates and the thickness of concrete and determining the heights of longitudinal side steel plates and the widths of bottom steel plates. Each composite reinforcement structure comprises the corresponding bottom steel plate, the two longitudinal side steel plates and a steel bushing case, each steel bushing case comprises two end blocking steel plates, and a plurality of unbonded prestress reinforcing steel bars are arranged in each steel bushing case. The unbonded prestress and steel-concrete composite reinforcement design method has the advantages that the steps are simple, the unbonded prestress and steel-concrete composite reinforcement design method is reasonable in design and convenient to implement, good service effects can be realized, the structural parameters of the bridge composite reinforcement structures can be easily, conveniently and quickly determined, the bridge composite reinforcement structures designed by the aid of the unbonded prestress and steel-concrete composite reinforcement design method are economical and practical, and good reinforcement effects can be realized by the bridge composite reinforcement structures.