Service data transmission method and device

A service data transmission method and device, used for solving the problem in the prior art that the data transmission success rate is not high and the user experience is reduced in methods for a UE to perform transmission on an LTE-U carrier cell via carrier aggregation means. The method of the present invention comprises: a sending device sends service data via a first cell on unlicensed spectrum; after determining that the first cell is not able to satisfy transmission requirements for the service data, the sending device determines a second cell; the sending device sends the service data via the determined second cell. In the present invention, another cell used for sending service data is determined after a cell on unlicensed spectrum is not able to satisfy transmission requirements for the service data, the data transmission success rate is increased, and the user experience is thereby improved.