The present disclosure provides a method and a device in a User Equipment (UE) and a base station used for wireless communications. The UE receives first information; determines first sub-information out of the M piece(s) of sub-information; receives a first radio signal in a first time-frequency resource set; the first information comprises the M piece(s) of sub-information, each of the M piece(s) of sub-information indicates a reference signal group, and a reference signal group comprises at least one reference signal. The first sub-information indicates a first reference signal group. A reference signal in a reference signal group indicated by at least one of the M piece(s) of sub-information is transmitted by a first serving cell, and the first serving cell is not added by the UE. The above method not only obtains performance advancement brought by serving cell handover, but also avoid time delay and service interrupt.