The present invention discloses a method for transmitting control information. Downlink control information is categorized into common control information and dedicated control information. A physical broadcast channel is extended by dividing a common control channel domain into a plurality of narrowband sub-control channel domains by adding a position identifier. Before a connection is established, the common control information is sent, according to the position identifier, in each sub-control channel domain of the common control channel domain. After the connection is established, a sub-control channel domain with a channel state that complies with a set standard is selected, according to a channel state of each sub-control channel domain, for sending the dedicated control information.