The present invention relates to the field of communications technologies, and in particular, to a data packet sending method and apparatus in an Internet Protocol IP version v6 network, so as to resolve a problem that a data packet may be always discarded before a PMTU of a path is probed in a current IPv6 network. The method includes: before a PMTU of a path is probed, sending a data packet according to a minimum MTU stipulated in the IPv6 protocol; and after the PMTU of the path is probed, sending a subsequent data packet on the path according to the probed PMTU of the path. The method ensures that the data packet can pass through a network device having any MTU on the path, so as to ensure that the data packet can be received by a destination receive end.