Abstract: The disclosure provides a neighbouring cell optimization method and a mobile communication system, which belong to the communication field. The method comprises: establishing an IUR connection between a first Radio Network Controller (RNC) and a second RNC; after the IUR connection is established successfully, the first RNC sending neighbouring cell information to the second RNC; and the second RNC performing automatic neighbouring cell optimization according to the neighbouring cell information. With the disclosure, the neighbouring cell information between two RNCs is updated in time, therefore the RNC is enabled to optimize the neighbouring cell in time, and a timely cell handover performed by User Equipment (UE) is ensured, which provides a basis for ensuring call continuity of the UE.