A calibration method for calibrating a plurality of remote radio units, RRUs, within a sub-cluster, the method comprising: receiving, by a control apparatus of each remote radio unit of said plurality, resource configuration information sent by a centralized control apparatus, wherein a time-frequency resource indicated by the resource configuration information is used to send and receive a calibration signal between each RRU and n other of the RRUs, the n other RRUs associated with each RRU are RRUs in a calibration path topology determined by the centralized control apparatus, a quantity of hops of a calibration path between each RRU and each of its associated n other RRUs is 1, and a quantity of hops of a shortest calibration path between any two RRUs in the calibration path topology is less than or equal to a preset hop quantity threshold, wherein n is a natural number greater than 1; controlling, by the control apparatus of each RRU based on the respective resource configuration information, each RRU to send and receive a calibration signal on the time-frequency resource; obtaining, by the control apparatus of each RRU, m groups of path information based on the calibration signal sent and received by each RRU, wherein m=1, or m=M, M is a quantity of channels of each respective RRU, and each of the m groups of path information comprises path information of n calibration paths between one channel of each RRU and its associated n other RRUs; obtaining, by the control apparatus of each RRU, m calibration coefficients based on the respective m groups of path information; and compensating, by the control apparatus of each RRU, the M channels of the respective RRU by using the m calibration coefficients. receiving, by a control apparatus of each remote radio unit of said plurality, resource configuration information sent by a centralized control apparatus, wherein a time-frequency resource indicated by the resource configuration information is used to send and receive a calibration signal between each RRU and n other of the RRUs, the n other RRUs associated with each RRU are RRUs in a calibration path topology determined by the centralized control apparatus, a quantity of hops of a calibration path between each RRU and each of its associated n other RRUs is 1, and a quantity of hops of a shortest calibration path between any two RRUs in the calibration path topology is less than or equal to a preset hop quantity threshold, wherein n is a natural number greater than 1; controlling, by the control apparatus of each RRU based on the respective resource configuration information, each RRU to send and receive a calibration signal on the time-frequency resource; obtaining, by the control apparatus of each RRU, m groups of path information based on the calibration signal sent and received by each RRU, wherein m=1, or m=M, M is a quantity of channels of each respective RRU, and each of the m groups of path information comprises path information of n calibration paths between one channel of each RRU and its associated n other RRUs; obtaining, by the control apparatus of each RRU, m calibration coefficients based on the respective m groups of path information; and compensating, by the control apparatus of each RRU, the M channels of the respective RRU by using the m calibration coefficients.