A data transmission method includes obtaining a user equipment route selection policy (USRP) rule parameter of a started application, establishing a first protocol data unit (PDU) session corresponding to the started application with a network device through the modem module when no PDU session parameter matching the URSP rule parameter exists in the mapping table, adding an interface name of the first PDU session to the routing table, adding a mapping relationship between the session parameter of the first PDU session and the interface name of the first PDU session to the mapping table, and routing to-be-transmitted data of the started application to the first PDU session by using the interface name of the first PDU session.