A random access method, the method comprising the following method steps: • sending, by a second network device, a first message to a first network device, wherein the first message comprises a radio resource control, RRC, connection reconfiguration message, wherein: ∘ the RRC connection reconfiguration message is used to indicate a primary serving cell of the second network device for a user equipment, and ∘ the RRC connection reconfiguration message includes a BWP identifier, wherein a BWP corresponding to the BWP identifer is an active BWP in the primary serving cell of the second network device, the active BWP including an active uplink BWP and an active downlink BWP; • receiving, by the first network device, the first message from the second network device; • sending, by the first network device, the RRC connection reconfiguration message to the user equipment; • receiving (step 4101), by user equipment, the RRC connection reconfiguration message from the first network device; • sending (step 41021a), by the user equipment, a random access preamble to the second network device on the active uplink BWP; • receiving (step 41022a), by the user equipment, on the active downlink BWP a RAR message from the second network device, the RAR message including an UL grant; and • performing (step 41023a), by the user equipment, uplink transmission on the active uplink BWP, wherein a physical resource used for the uplink transmission is a physical resource indicated by the UL grant. • sending, by a second network device, a first message to a first network device, wherein the first message comprises a radio resource control, RRC, connection reconfiguration message, wherein: ∘ the RRC connection reconfiguration message is used to indicate a primary serving cell of the second network device for a user equipment, and ∘ the RRC connection reconfiguration message includes a BWP identifier, wherein a BWP corresponding to the BWP identifer is an active BWP in the primary serving cell of the second network device, the active BWP including an active uplink BWP and an active downlink BWP; ∘ the RRC connection reconfiguration message is used to indicate a primary serving cell of the second network device for a user equipment, and ∘ the RRC connection reconfiguration message includes a BWP identifier, wherein a BWP corresponding to the BWP identifer is an active BWP in the primary serving cell of the second network device, the active BWP including an active uplink BWP and an active downlink BWP; • receiving, by the first network device, the first message from the second network device; • sending, by the first network device, the RRC connection reconfiguration message to the user equipment; • receiving (step 4101), by user equipment, the RRC connection reconfiguration message from the first network device; • sending (step 41021a), by the user equipment, a random access preamble to the second network device on the active uplink BWP; • receiving (step 41022a), by the user equipment, on the active downlink BWP a RAR message from the second network device, the RAR message including an UL grant; and • performing (step 41023a), by the user equipment, uplink transmission on the active uplink BWP, wherein a physical resource used for the uplink transmission is a physical resource indicated by the UL grant. <EOS>