The present disclosure discloses a method and system for transmitting downlink control information, for solving the problem of how to indicate a transmission scheme when a cyclic redundancy check code in the downlink control channel is scrambled with the semi-persistently scheduled cell radio network temporary identifier. In order to support the bi-flow beam forming technology in the LTE-A R9, the present disclosure provides a downlink control information Format 1A, which may, when the cyclic redundancy check code in the downlink control channel is scrambled with the semi-persistently scheduled cell radio network temporary identifier, indicates a method for transmitting downlink control information, for example, single-layer transmission, transmit diversity, or a transmission scheme simultaneously involving single-layer transmission and transmit diversity, which guarantees flexibility of system schedule. The present disclosure adds no signaling overhead and has good adaptability with the LTE R8.