A network device sends configuration information to a terminal device, where the configuration information includes a scale factor corresponding to each aggregation level in a first aggregation level set; the network device sends DCI in a first DCI format to the terminal device, where an aggregation level corresponding to the DCI in the first DCI format is an aggregation level in the first aggregation level set. The terminal device receives the configuration information, determines, based on the scale factor corresponding to each aggregation level in the first aggregation level set, a quantity of candidate PDCCHs corresponding to each aggregation level in the first aggregation level set; the terminal device receives the DCI in the first DCI format based on the quantity of candidate PDCCHs corresponding to each aggregation level in the first aggregation level set.