TPO (thermoplastic olefin) composite for rear bumper back beams was developed. In this study, the composition of PP (polypropylene), rubber and mineral fillers was optimized to minimize the intrusion and the failure after crash. The optimization of the composition was achieved using the mixture design of experiments. The physical properties of TPO composites with various compositions were investigated and the effect of each material on the crash performance of back beam was studied through CAE (computer-aided engineering). The back beams made of the optimized TPO composite for a subcompact car were prepared for the ECE 42 crash test and the TPO-based back beam showed even better performance than conventional PC/PBT-based counterpart. In addition, the newly developed composite has delivered a 15 ~ 40% cost saving and 4 ~ 10% weight reduction versus conventional PC/PBT and GMT (glass mat-reinforced thermoplastic).