Abstract: In order to provide a reference for connectors’ local strengthening design of prestressed steel-concrete composite beams, the analytical solutions of load effects under prestressing axial load were deduced by energy-variation principle, in which the influence of shear lag and slip between the steel girder and concrete slab were considered. The numerical results agreed well with the test results. Based on the analytical results, the mechanism of slip between the steel girder and concrete slab was developed. It was shown that the slip deformation and the longitudinal shear force at the anchorage zone were much larger than those at the middle span, which may control the design of the shear connectors if the stretching control stress was too large. The calculation method of longitudinal shear force suggested in this paper can be used in connectors’ local strengthening design of prestressed steel-concrete composite beams.