Abstract: Under the action of long-time loading, creep and shrinkage deformation will come to being in the high-strength concrete of a prestressed steel composite beam with flexible shear connectors, thus causing the stress to redistribute in concrete slab and steel beam. Introducing a comprehensive method combining the age-adjusted effective modulus with mean stress and considering the deformation relationships among the concrete slab, steel beam and prestressed cable, two mathematic models are developed separately for the elastic analysis of the simply supported composite beam and the viscoelastic analysis of the same beam with the creep effect on the concrete taken into account. With the numerical computation/analysis program discussed through an example, the moment, strain variation, deformation properties and the interface slip of the simply supported composite beam are analyzed.