The objective of this research is to understand the crashworthiness performance of composite inserts in vehicle structure and to improve the numerical model of steel-composite combined structure for providing better prediction in the design process of composite inserts. A simplified steel-composite combined beam structure is used for three-point bending tests. Epoxy-based structural foam and 33% short glass fiber reinforced nylon composite insert are considered as composite fillers in empty sections of double hat-type steel beam structure. Four cases based on the different combination of composite materials are considered.In the series of physical three-point bending tests, the force-displacement (F-D) curves and material behaviors are investigated. The test results show that the composite insert greatly contributes to improve the crashworthiness of beam structure as well as to reduce the vehicle weight. Especially, the adhesive failure of structural foam and the brittle fracture mode of composite insert are greatly influential to the resistance force level in the three-point bending test. In the numerical study, a concern is to build a practical FE model, which can be used in full-scale vehicle crash simulation. The parametric study shows that parameters related to material and contact types are critical to simulate the adhesive failure of structural foam and the brittle fracture of composite insert. The final simulation results show good agreement with the physical tests.