Because vehicles run in high speed environments, it is difficult to establish the topology of the network. Moreover, data transmission may be interrupted by the handoff of various APs. This study established the network of roadside-to-vehicle (R2V) environment, and used the DSRC (dedicated short range communication) to achieve seamless handoff control on a streaming service. To achieve this goal, we first used the GPS (global positioning system) to collect vehicular information (e.g., speed, direction, and location), and subsequently exchanged the parameter of vehicular information at both ends by DSRC. Therefore, the computer in the vehicle can predict the link expiration time (LET) between two mobile nodes. Furthermore, this study used two cases of handoff in vehicular networks. One case was non-overlapping handoff, and the other case was overlapping handoff. A simple formula was designed to calculate vehicular total buffer size in these two cases, and to adjust the data flow to the receiver. Finally, we used the network simulator to simulate the actual situation of vehicular motion and network transmission. This study proved the accuracy and feasibility of mechanism through the simulation result. This study achieved the streaming of seamless handoff control in the network of R2V.