The invention provides an IOV (Internet of vehicles) data transmission method and device based on a software definition network, and an IOV comprises an application layer, a control layer, and a data forwarding layer. The control layer carries out the information interaction with the application layer and the data forwarding layer through a northbound interface and a southbound interface. The method comprises the steps that control layer equipment obtains the position information and future track information of all data forwarding layer equipment; the control layer equipment judges whether to transmit a data message through a long-distance cellular wireless communication network or not when the control layer equipment knows that the data forwarding layer equipment needs to send a data message: indicating the data forwarding layer equipment to carry out the forwarding of the data message from a cellular interface if the data message needs to be transmitted through the long-distance cellular wireless communication network, or else, generating a flow table corresponding to the data message according to the position information of the data forwarding layer equipment and the future track information, and transmitting the flow table to the data forwarding layer equipment, so as to enable the data forwarding layer equipment to carry out the forwarding of the data message, and achieve the short-distance wireless communication of the data message.