A method for determining temporary Base Station (BS) Identifiers (IDs) to efficiently set a multi-BS Multiple Input Multiple Output (MIMO) transmission mode and an apparatus for implementing the same in a broadband wireless access system are disclosed. To perform a multi-BS MIMO operation, a Mobile Station (MS) receives a first broadcast message including system information about a plurality of neighbor BSs from a serving BS, receives a second broadcast message including BS set information from the serving BS, the BS set information specifying indexes of one or more neighbor BSs which can be involved in the multi-BS MIMO operation among the plurality of neighbor BSs, and determines a temporary BS ID of each BS included in the BS set information using the specified indexes.