This paper presents a three-dimensional finite element (FE) anaytical approach for the simulation of steel-concrete composite beams. To simulate key problem, the interfacial behavior between the steel girders and concrete slabs, an interface-slip model is applied in the analysis. Both simple-supported beam experiment and continuous composite beam experiment are simulated. The load-deflection relation and the slip between the steel girders and concrete slabs as well as the strain of the steel girder and reinforcing bar in concrete are obtained from the FE analyses, and found to match well with the corresponding experimental results. The proposed nonlinear FE analysis method is capable of simulating the mechanical behaviors of steel-concrete composite beam.