Data transmission method and data transmission system

Provided are a data transmission method and a data transmission system; the data transmission method comprises: according to a service request received by the network side or triggered by the network side, it is determined whether to use direct-connection communications as a data transmission means, and if the determined result is "yes", then the data source node and data-receiving destination node corresponding to said service request are determined; according to the physical domain network selection principle and the business model domain network selection principle, a bearer network node is selected corresponding to said data source node and said data-receiving destination node; according to said bearer network node, data source node, and data-receiving destination node, the network structure corresponding to the direct-connection communications data transmission means is determined. Thus it is possible to establish an optimized direct-connection communications network model in order to resolve trust and incentive problems in direct-connection communications networks.