The present invention discloses a method and device for transmitting downlink information in a multi-carrier aggregation system. The Method includes: a base station side sends a downlink subframe to a terminal side, wherein, the physical downlink control channel (PDCCH) in the downlink subframe is used for bearing more than one piece of downlink control indicating information and the carrier scheduling indicating information corresponding to each downlink control indicating information. It solves the problem in the prior art of indefinite identification at the terminal side because the length of DCI may be same due to the difference of the bandwidths of carriers in the carrier aggregation system.