Embodiments of the present invention relate to the communications field, and provide a method, an apparatus, and a system for configuring a search space, to implement that a PDCCH carrying uplink-downlink configuration information can be sent normally, so that user equipment UE can receive uplink-downlink configuration information of a base station in time, thereby ensuring that the UE can complete data transmission according to the uplink-downlink configuration information, and improving user experience. The method includes: configuring, by a base station, a first subframe set, where a subframe in the first subframe set is a downlink subframe or a special subframe; configuring, by the base station, a first common search space CSS in the subframe in the first subframe set; and sending, by the base station to user equipment UE, a physical downlink control channel PDCCH carrying uplink-downlink configuration information, where the PDCCH is a PDCCH in the first CSS.