Rear-end accident is one of the most important collision modes in China, which often leads to severe accident consequences due to the high collision velocity. Autonomous Emergency Braking (AEB) System could perform emergency brake automatically in dangerous situation and mitigate the consequence. This study focused on the analysis of the rear-end accidents in China in order to discuss about the parameters of Time-to-Collision (TTC) of AEB and the potential effectiveness. A sample of 84 accidents was in-depth investigated and reconstructed, providing a comprehensive set of data describing the pre-crash matrix. Each accident in this sample is reconstructed and modeled numerically by the simulation tool PC-Crash. In parallel, a model representing the function of an AEB system has been established. This AEB system applies partial braking when the TTC ≤ TTC1 and full braking when the TTC ≤ TTC2. Lastly, the AEB system's model is coupled to the kinematic of the vehicle in simulation for virtual trajectories preceding the collision point to evaluate the potential effectiveness of different combinations of TTC, according to the typical scenarios, delta V and collision velocity. After the simulations of 4284 run with 51 combination of the parameters based on 84 accidents, the results show that the combination of TTC1=1.0s and TTC2=0.6s is the best with the overall collision avoidance of 91.7% and the collision velocity reduction effectiveness of 4.726, while the combinations with larger TTC could bring no further benefits in collision avoidance. Furthermore, there are 7 cases, where the AEB system couldn't avoid the crash for special reasons. Conclusion: The research on the AEB system in this study has been carried out based on real-world road traffic accidents in China. The results could fit to China's actual traffic situation, which would provide a reliable basis for R&D of AEB system in China.