A multipath data transmission method and device are provided, where a multipath proxy client and a multipath proxy gateway establish at least two multipath data subflows based on a first internet protocol (IP) address, and perform multipath data subflow data transmission. Based on the first IP address for establishing the at least two multipath data subflows between the multipath proxy client and the multipath proxy gateway, the multipath proxy gateway establishes a TCP connection to and performs TCP-based data transmission with an application server to be accessed by the multipath proxy client. MPTCP-based multipath data transmission based on IP address information of the multipath proxy client is implemented through proxy of the multipath proxy client and the multipath proxy gateway.