A method for receiving downlink control information, DCI, performed by a user equipment, the method comprising: determining a first set of physical downlink control channel, PDCCH, candidate number of a first set of aggregation level, AL, including one or more candidate numbers at one or more aggregation levels for receiving a first DCI (203, 601, 604, 607, 610, 613, 616, 619, 2103); and receiving the first DCI (203, 601, 604, 607, 610, 613, 616, 619, 2103) according to the first set of PDCCH candidate number and the first set of AL on a first cell, wherein the first DCI (203, 601, 604, 607, 610, 613, 616, 619, 2103) is configured for scheduling physical downlink shared channels, PDSCHs, (207, 208, 602, 603, 605, 606, 608, 609, 611, 612, 614, 615, 617, 618, 620, 621, 2102, 2105) on a plurality of cells, the plurality of cells comprises a second cell and a third cell, and the first set of PDCCH candidate number and the first set of AL are corresponding to a search space with a first identity, and wherein the method further comprising: receiving the PDSCHs (207, 208, 602, 603, 605, 606, 608, 609, 611, 612, 614, 615, 617, 618, 620, 621, 2102, 2105) on the second cell and the third cell according to the first DCI; characterized by further comprising: transmitting a HARQ-ACK feedback for the PDSCHs (207, 208, 602, 603, 605, 606, 608, 609, 611, 612, 614, 615, 617, 618, 620, 621, 2102, 2105) on a first slot, wherein a second slot is configured for receiving one of the PDSCHs (207, 208, 602, 603, 605, 606, 608, 609, 611, 612, 614, 615, 617, 618, 620, 621, 2102, 2105) on one of the plurality of cells, the first slot is the (n+K1)th slot, the second slot is the nth slot, and the value K1 is indicated by the first DCI (203, 601, 604, 607, 610, 613, 616, 619, 2103), wherein the second slot is a latest slot among at least one slot configured for receiving the PDSCHs (207, 208, 602, 603, 605, 606, 608, 609, 611, 612, 614, 615, 617, 618, 620, 621, 2102, 2105) respectively on the plurality of cells. determining a first set of physical downlink control channel, PDCCH, candidate number of a first set of aggregation level, AL, including one or more candidate numbers at one or more aggregation levels for receiving a first DCI (203, 601, 604, 607, 610, 613, 616, 619, 2103); and receiving the first DCI (203, 601, 604, 607, 610, 613, 616, 619, 2103) according to the first set of PDCCH candidate number and the first set of AL on a first cell, wherein the first DCI (203, 601, 604, 607, 610, 613, 616, 619, 2103) is configured for scheduling physical downlink shared channels, PDSCHs, (207, 208, 602, 603, 605, 606, 608, 609, 611, 612, 614, 615, 617, 618, 620, 621, 2102, 2105) on a plurality of cells, the plurality of cells comprises a second cell and a third cell, and the first set of PDCCH candidate number and the first set of AL are corresponding to a search space with a first identity, and wherein the method further comprising: receiving the PDSCHs (207, 208, 602, 603, 605, 606, 608, 609, 611, 612, 614, 615, 617, 618, 620, 621, 2102, 2105) on the second cell and the third cell according to the first DCI; characterized by further comprising: transmitting a HARQ-ACK feedback for the PDSCHs (207, 208, 602, 603, 605, 606, 608, 609, 611, 612, 614, 615, 617, 618, 620, 621, 2102, 2105) on a first slot, wherein a second slot is configured for receiving one of the PDSCHs (207, 208, 602, 603, 605, 606, 608, 609, 611, 612, 614, 615, 617, 618, 620, 621, 2102, 2105) on one of the plurality of cells, the first slot is the (n+K1)th slot, the second slot is the nth slot, and the value K1 is indicated by the first DCI (203, 601, 604, 607, 610, 613, 616, 619, 2103), wherein the second slot is a latest slot among at least one slot configured for receiving the PDSCHs (207, 208, 602, 603, 605, 606, 608, 609, 611, 612, 614, 615, 617, 618, 620, 621, 2102, 2105) respectively on the plurality of cells. receiving the PDSCHs (207, 208, 602, 603, 605, 606, 608, 609, 611, 612, 614, 615, 617, 618, 620, 621, 2102, 2105) on the second cell and the third cell according to the first DCI; characterized by further comprising: transmitting a HARQ-ACK feedback for the PDSCHs (207, 208, 602, 603, 605, 606, 608, 609, 611, 612, 614, 615, 617, 618, 620, 621, 2102, 2105) on a first slot, wherein a second slot is configured for receiving one of the PDSCHs (207, 208, 602, 603, 605, 606, 608, 609, 611, 612, 614, 615, 617, 618, 620, 621, 2102, 2105) on one of the plurality of cells, the first slot is the (n+K1)th slot, the second slot is the nth slot, and the value K1 is indicated by the first DCI (203, 601, 604, 607, 610, 613, 616, 619, 2103), wherein the second slot is a latest slot among at least one slot configured for receiving the PDSCHs (207, 208, 602, 603, 605, 606, 608, 609, 611, 612, 614, 615, 617, 618, 620, 621, 2102, 2105) respectively on the plurality of cells. transmitting a HARQ-ACK feedback for the PDSCHs (207, 208, 602, 603, 605, 606, 608, 609, 611, 612, 614, 615, 617, 618, 620, 621, 2102, 2105) on a first slot, wherein a second slot is configured for receiving one of the PDSCHs (207, 208, 602, 603, 605, 606, 608, 609, 611, 612, 614, 615, 617, 618, 620, 621, 2102, 2105) on one of the plurality of cells, the first slot is the (n+K1)th slot, the second slot is the nth slot, and the value K1 is indicated by the first DCI (203, 601, 604, 607, 610, 613, 616, 619, 2103), wherein the second slot is a latest slot among at least one slot configured for receiving the PDSCHs (207, 208, 602, 603, 605, 606, 608, 609, 611, 612, 614, 615, 617, 618, 620, 621, 2102, 2105) respectively on the plurality of cells.