Under the DSRC architecture, we propose a clusterbased multi-channel communication scheme to provision the Quality of Service (QoS), especially the real-time delivery of safety traffics, over the Vehicle Ad Hoc Networks (VANET). Our scheme integrates the clustering algorithm, contention-free, and contention-based MAC to support the real-time transmission of safety-messages. We develop the analytical model to conduct the safety message delay analyses. Our analyses show that our scheme can guarantee the real-time transmission of safety messages. The analytical results are also verified by our simulation experiments.