A data transmission method and a device are disclosed. The method includes: receiving, by a third-party node in a specified first spectrum, a request message sent by a network side device that belongs to an operator different from an operator of the third-party node, where the request message is used to request the third-party node to forward data that is transmitted between the network side device and a terminal served by the network side device; returning, by the third-party node, a response message to the network side device in the first spectrum after the third-party node determines to accept the request of the network side device; and forwarding, by the third-party node in a second spectrum, the data that is transmitted between the network side device and the terminal, where the second spectrum is a spectrum of the operator to which the network side device belongs.