Abstract: To present the calculation model for the interface slip and deflection curve considering the interface slip of a steel-concrete composite beam, on the basis of Bernoulli beam theory and the linear shear-slip model of shear connectors, the method to calculate the distribution of the bending moment and shearing force of cross sections by total differentiation, as well as a global-local bending model suitable for composite beam deformation analysis are proposed by means of the equilibrium equation, geometric equation and constitutive equation of the beam. Furthermore, the control equation for the interface slip and deflection of the composite beam is put forward using the distribution coefficient of global moment. The formulas for the interface slip and deflection curve equation of a simply supported composite beam under a uniform distributed load, a concentrated load at mid-span and a symmetric concentrated load are proposed by applying the global-local bending model to the deformation analysis of the simply supported composite beam and by calculating with MAPLE software. Compared with the existing test data, the calculation results meet well with the actual conditions.