Abstract: The bending capacity of prestressed steel-concrete composite beam which is a new structure is influenced by many parameters.The concrete flange and the steel of the composite beams can not work together completely when bearing load and some relative slip will occur in the interface between them,which is bad for the materials mechanical properties.So it is necessary to research the interface slip of the prestressed steel-concrete composite beam.According to the experimental results,the regularity of slip distribution and its development are analyzed in the paper.The research results show that the interface slip increases with load,and increases slowly in the elastic stage but quickly in the ductility stage;the relative slip will cause strain difference on the interface of the steel and concrete.