The invention discloses a timing synchronization method in a User Equipment (UE) which is served in a first cell of a first synchronous communication network and also located in a second cell of a second synchronous communication network. The method comprises receiving a message from a communication node of the first network, the message including clock offsets of the first cell and the second cell or timing difference there between, and calculating downlink synchronization of the second cell from downlink synchronization of the first cell and the clock offsets/timing difference.