A method for transmitting Physical Downlink Control Channel (PDCCH) information, a method for determining PDCCH search space and devices thereof are disclosed in the present embodiments. The method for determining PDCCH search space includes the following step: Node B (NB) determines the different search spaces corresponding to different PDCCHs according to Carrier Indicator (CI) information. By applying the technical solution provided in the embodiments of the present invention, the CI information is introduced in the search space determining process, so that different search spaces can be allocated to the cross-carrier PDCCHs of one User Equipment (UE) and the NB and UE are able to exactly determine the search spaces of PDCCHs in each downlink carrier, therefore reducing the blocking probability during PDCCH scheduling process and improving the reliability of PDCCH transmission.