A packet transmission method includes: receiving packets on a plurality of subflow connections of a multipath transmission control protocol (MPTCP) connection, and determining, based on the received packets, that packets at an MPTCP layer are out of order; determining that a blocking packet causing out-of-order is not received within a tolerance time, where the tolerance time is less than a largest RTO in RTOs of the plurality of subflow connections; and sending, by the network component, a retransmission instruction packet of the blocking packet on a target subflow connection in the plurality of subflow connections, where the retransmission instruction packet is used to instruct a sending device of the blocking packet to retransmit the blocking packet. Thus, there is no need to trigger retransmission after a subflow RTO expires, thereby shortening a delay.