A session establishment method, characterized by comprising: determining, by a session management function, SMF, entity, that a packet data unit, PDU, session is to be established to switch a terminal from a broadcast path to a unicast path; sending, by the SMF, entity, a PDU session establishment request message to the terminal, wherein the PDU session establishment request message is used to request to establish the PDU session; and receiving, by the SMF entity, a PDU session establishment response message from the terminal; wherein the method further comprises: providing, by the SMF entity, session establishment assistance information of the PDU session to the terminal, wherein the session establishment assistance information of the PDU session comprises one or more of a broadcast session identifier and a group identifier, the broadcast session identifier and the group identifier correspond to the broadcast path; wherein the providing, by the SMF entity, session establishment assistance information of the PDU session to the terminal, comprises: including the session establishment assistance information of the PDU session in the PDU session establishment request message; or separately sending, by the SMF entity, the session establishment assistance information of the PDU session to the terminal. wherein the method further comprises: selecting, by the SMF entity based on the broadcast session identifier, a user plane function, UPF, entity corresponding to the broadcast session, and sending a user plane session request to the UPF entity corresponding to the broadcast session, wherein the user plane session request comprises user plane forwarding rule information of the PDU session; or selecting, by the SMF entity based on the group identifier, a UPF entity corresponding to the group identifier, and sending a user plane session request to the UPF entity corresponding to the group identifier, wherein the user plane session request comprises user plane forwarding rule information of the PDU session. determining, by a session management function, SMF, entity, that a packet data unit, PDU, session is to be established to switch a terminal from a broadcast path to a unicast path; sending, by the SMF, entity, a PDU session establishment request message to the terminal, wherein the PDU session establishment request message is used to request to establish the PDU session; and receiving, by the SMF entity, a PDU session establishment response message from the terminal; wherein the method further comprises: providing, by the SMF entity, session establishment assistance information of the PDU session to the terminal, wherein the session establishment assistance information of the PDU session comprises one or more of a broadcast session identifier and a group identifier, the broadcast session identifier and the group identifier correspond to the broadcast path; wherein the providing, by the SMF entity, session establishment assistance information of the PDU session to the terminal, comprises: including the session establishment assistance information of the PDU session in the PDU session establishment request message; or separately sending, by the SMF entity, the session establishment assistance information of the PDU session to the terminal. wherein the method further comprises: selecting, by the SMF entity based on the broadcast session identifier, a user plane function, UPF, entity corresponding to the broadcast session, and sending a user plane session request to the UPF entity corresponding to the broadcast session, wherein the user plane session request comprises user plane forwarding rule information of the PDU session; or selecting, by the SMF entity based on the group identifier, a UPF entity corresponding to the group identifier, and sending a user plane session request to the UPF entity corresponding to the group identifier, wherein the user plane session request comprises user plane forwarding rule information of the PDU session. including the session establishment assistance information of the PDU session in the PDU session establishment request message; or separately sending, by the SMF entity, the session establishment assistance information of the PDU session to the terminal. wherein the method further comprises: selecting, by the SMF entity based on the broadcast session identifier, a user plane function, UPF, entity corresponding to the broadcast session, and sending a user plane session request to the UPF entity corresponding to the broadcast session, wherein the user plane session request comprises user plane forwarding rule information of the PDU session; or selecting, by the SMF entity based on the group identifier, a UPF entity corresponding to the group identifier, and sending a user plane session request to the UPF entity corresponding to the group identifier, wherein the user plane session request comprises user plane forwarding rule information of the PDU session. selecting, by the SMF entity based on the broadcast session identifier, a user plane function, UPF, entity corresponding to the broadcast session, and sending a user plane session request to the UPF entity corresponding to the broadcast session, wherein the user plane session request comprises user plane forwarding rule information of the PDU session; or selecting, by the SMF entity based on the group identifier, a UPF entity corresponding to the group identifier, and sending a user plane session request to the UPF entity corresponding to the group identifier, wherein the user plane session request comprises user plane forwarding rule information of the PDU session.