A data transmission method and apparatus are provided. One example method involves establishing two tunnels between an access network device and a user plane function network element, where the two tunnels may be tunnels used for downlink data transmission or tunnels used for uplink data transmission. When communicating with the user plane function network element, the access network device may transmit two data packets. In this way, when one data packet is lost, the receive end may further receive the other data packet.