A physical downlink control channel processing method performed by a first device or a second device, the method comprising: • determining a search space based on a first radio network temporary identifier, wherein the search space is a set of M candidate physical downlink control channels, and M is an integer greater than or equal to 1 (S 101, S201); and • detecting a target physical downlink control channel from the search space based on a second radio network temporary identifier (S 102, S 202), wherein the first radio network temporary identifier is a radio network temporary identifier of the first device or the second device, the second radio network temporary identifier is the radio network temporary identifier of the second device, first downlink control information carried by the target physical downlink control channel is information that is scrambled by using the second radio network temporary identifier and that is used to schedule the second device, and the second device communicates with a network by using the first device, • wherein the method further comprises: determining at least one time unit based on a further identifier of the second device, wherein the determining at least one time unit based on the further identifier of the second device comprises: ▪determining, from a plurality of time units, at least one time unit whose index satisfies the following formula: i mod n2 = identity mod n2, wherein n2 is an integer and n2 ≤ N; i is an index of each of the plurality of time units, wherein i = 0, 1,..., N-1, and N is a quantity of the plurality of time units; the identity is the further identifier of the second device; and n2 is predefined, and is configured by the network device or determined by the first device; the determining the search space based on the first radio network temporary identifier comprises: ▪determining the search space in the at least one time unit based on the first radio network temporary identifier. • determining a search space based on a first radio network temporary identifier, wherein the search space is a set of M candidate physical downlink control channels, and M is an integer greater than or equal to 1 (S 101, S201); and • detecting a target physical downlink control channel from the search space based on a second radio network temporary identifier (S 102, S 202), wherein the first radio network temporary identifier is a radio network temporary identifier of the first device or the second device, the second radio network temporary identifier is the radio network temporary identifier of the second device, first downlink control information carried by the target physical downlink control channel is information that is scrambled by using the second radio network temporary identifier and that is used to schedule the second device, and the second device communicates with a network by using the first device, • wherein the method further comprises: determining at least one time unit based on a further identifier of the second device, wherein the determining at least one time unit based on the further identifier of the second device comprises: ▪determining, from a plurality of time units, at least one time unit whose index satisfies the following formula: i mod n2 = identity mod n2, wherein n2 is an integer and n2 ≤ N; i is an index of each of the plurality of time units, wherein i = 0, 1,..., N-1, and N is a quantity of the plurality of time units; the identity is the further identifier of the second device; and n2 is predefined, and is configured by the network device or determined by the first device; the determining the search space based on the first radio network temporary identifier comprises: ▪determining the search space in the at least one time unit based on the first radio network temporary identifier. determining at least one time unit based on a further identifier of the second device, wherein the determining at least one time unit based on the further identifier of the second device comprises: ▪determining, from a plurality of time units, at least one time unit whose index satisfies the following formula: i mod n2 = identity mod n2, wherein n2 is an integer and n2 ≤ N; i is an index of each of the plurality of time units, wherein i = 0, 1,..., N-1, and N is a quantity of the plurality of time units; the identity is the further identifier of the second device; and n2 is predefined, and is configured by the network device or determined by the first device; ▪determining, from a plurality of time units, at least one time unit whose index satisfies the following formula: i mod n2 = identity mod n2, wherein n2 is an integer and n2 ≤ N; i is an index of each of the plurality of time units, wherein i = 0, 1,..., N-1, and N is a quantity of the plurality of time units; the identity is the further identifier of the second device; and n2 is predefined, and is configured by the network device or determined by the first device; the determining the search space based on the first radio network temporary identifier comprises: ▪determining the search space in the at least one time unit based on the first radio network temporary identifier. ▪determining the search space in the at least one time unit based on the first radio network temporary identifier.