A method for detecting downlink control information, comprising: when scheduling across carriers is enabled, determining by a user equipment a user-specific search space monitoring a physical downlink control channel, PDCCH, according to component carrier indexes, wherein the component carrier indexes include various component carriers implementing scheduling across carriers and being scheduled across carriers; and, relative positions among starting positions of the user-specific search spaces corresponding to various component carriers implementing scheduling across carriers and being scheduled across carriers are fixed; characterized in that: the step of determining by a user equipment a user-specific search space monitoring a physical downlink control channel according to component carrier indexes comprises: determining a control channel element, CCE, corresponding to a PDCCH candidate m in the user-specific search space S k according to the following formula: L ⋅ Y k + m + f L I ⁢ mod ⌊ N CCE, k / L ⌋ + i Y k = A ⋅ Y k - 1 ⁢ mod D; where i =0,..., L -1, m =0,..., M -1, M is the number of PDCCH candidates to be detected in the search space S k, k = └ n s /2┘, └ ┘ represents round down, n s is a timeslot number in a radio frame, Y -1 = n RNTI ≠ 0, A =39827, D=65537, n RNTI is a corresponding radio network temporary identifier, N CCE, k is the number of CCEs of a PDCCH control domain carried by the k th subframe, and f ( L, I) is a function with input thereof being component carrier index I and aggregation level L. when scheduling across carriers is enabled, determining by a user equipment a user-specific search space monitoring a physical downlink control channel, PDCCH, according to component carrier indexes, wherein the component carrier indexes include various component carriers implementing scheduling across carriers and being scheduled across carriers; and, relative positions among starting positions of the user-specific search spaces corresponding to various component carriers implementing scheduling across carriers and being scheduled across carriers are fixed; characterized in that: the step of determining by a user equipment a user-specific search space monitoring a physical downlink control channel according to component carrier indexes comprises: determining a control channel element, CCE, corresponding to a PDCCH candidate m in the user-specific search space S k according to the following formula: L ⋅ Y k + m + f L I ⁢ mod ⌊ N CCE, k / L ⌋ + i Y k = A ⋅ Y k - 1 ⁢ mod D; where i =0,..., L -1, m =0,..., M -1, M is the number of PDCCH candidates to be detected in the search space S k, k = └ n s /2┘, └ ┘ represents round down, n s is a timeslot number in a radio frame, Y -1 = n RNTI ≠ 0, A =39827, D=65537, n RNTI is a corresponding radio network temporary identifier, N CCE, k is the number of CCEs of a PDCCH control domain carried by the k th subframe, and f ( L, I) is a function with input thereof being component carrier index I and aggregation level L. the step of determining by a user equipment a user-specific search space monitoring a physical downlink control channel according to component carrier indexes comprises: determining a control channel element, CCE, corresponding to a PDCCH candidate m in the user-specific search space S k according to the following formula: L ⋅ Y k + m + f L I ⁢ mod ⌊ N CCE, k / L ⌋ + i Y k = A ⋅ Y k - 1 ⁢ mod D; where i =0,..., L -1, m =0,..., M -1, M is the number of PDCCH candidates to be detected in the search space S k, k = └ n s /2┘, └ ┘ represents round down, n s is a timeslot number in a radio frame, Y -1 = n RNTI ≠ 0, A =39827, D=65537, n RNTI is a corresponding radio network temporary identifier, N CCE, k is the number of CCEs of a PDCCH control domain carried by the k th subframe, and f ( L, I) is a function with input thereof being component carrier index I and aggregation level L. determining a control channel element, CCE, corresponding to a PDCCH candidate m in the user-specific search space S k according to the following formula: L ⋅ Y k + m + f L I ⁢ mod ⌊ N CCE, k / L ⌋ + i Y k = A ⋅ Y k - 1 ⁢ mod D; where i =0,..., L -1, m =0,..., M -1, M is the number of PDCCH candidates to be detected in the search space S k, k = └ n s /2┘, └ ┘ represents round down, n s is a timeslot number in a radio frame, Y -1 = n RNTI ≠ 0, A =39827, D=65537, n RNTI is a corresponding radio network temporary identifier, N CCE, k is the number of CCEs of a PDCCH control domain carried by the k th subframe, and f ( L, I) is a function with input thereof being component carrier index I and aggregation level L.