Communication method, device and system

The invention provides a communication method, device and system, and belongs to the technical field of communication. In the method, after a terminal and a first access network device finish time synchronization through a second message, the first access network device can still continue to send a first message to the terminal to indicate the time when the first access network device sends the first message. Thus, the terminal can continuously determine the time of the terminal synchronized with the first access network device according to the previously synchronized time, such as the time when the first access network device sends the second message, the time when the terminal receives the second message, and the time when the first access network device sends the first message. Therefore, the terminal and the access network equipment can keep time synchronization for a long time.