Embodiments of the present application provide a data transmission method, and the method is used for communication between UE and a base station on an unlicensed spectrum. The method includes: sending, by the UE, a data packet to the base station and starting a timer during a current COD of the base station; determining a first end moment of the current COD; pausing the timer at the first end moment; determining a second end moment of an LP in a next COD of the base station; resuming the timer at the second end moment; and receiving, before the resumed timer expires, a response message from the base station. In the embodiments of the present application, the UE suspends the timer at the end moment of the previous COD and resumes the timer at the end moment of the LP of the next COD.