PDU session establishment method and apparatus

A PDU session establishment method, comprising:

• receiving, by a terminal device in a process of establishing a public data network (PDN) connection in a first system, an access type that is sent by a core network device and that corresponds to the PDN connection in a second system;
• when the terminal device moves to the second system, establishing, by the terminal device, a protocol data unit (PDU) session in the second system via an access network indicated by the access type, wherein the PDU session is associated with the PDN connection;
• determining, by the terminal device, to use a terminal device route selection policy (URSP) rule corresponding to an application of the PDU session;
• and
• when a parameter of the PDU session does not match the URSP rule of the application, skipping, by the terminal device, binding the application to the PDU session, or releasing the PDU session.