In vehicle nodes dense networks, the existing IEEE 802.11p protocol cannot guarantee effective data transmission efficiency because of the aggravation of the collision between nodes. In the cluster-based network, to ensure the effective transmission of data packets, this paper proposes an improved IEEE 802.11p protocol combined with TDMA, which is suitable for dense scenarios. At the same time, the performance of the improved mechanism is analyzed by establishing a two-dimensional Markov model, and the performance indexes such as system transmission rate and delay are obtained. Finally, the improved mechanism is simulated and evaluated, and the influence of the number of nodes and cluster heads on the system communication performance is studied. To a certain extent, it can guide the deployment of roadside facilities and the optimization of cluster heads in VANET.