Internet of Vehicles (IoV) is a significant 5G application scenario. As it developed rapidly, more and more vehicles are connected to Internet of Vehicles. The data security and privacy are the premises to ensure its service quality in an open communication network. This paper proposes IoV-SDCM, a secure data communication model in IoV. It includes a self-organizing relay forwarding network and an assured delivery mechanism. The relay forwarding network is used for constructing a dynamic collaboration network with the vehicle as the node. The security delivery mechanism is that network coding is used for data fragmentation and re-encoding to improve network communication reliability. Homomorphic encryption is used to encrypt and protect the encoding vector, improving information leakage and anticollusion attacks. The theoretical proof proves that the model has the ability of data transmission confidentiality and better antiattack capabilities, while it has privacy protection capabilities. Furthermore, the experiment verifies that the model also has the advantage of high and stable data delivery efficiency.