10. A proximity service (ProSe) information transmission method, comprising: acquiring, by a monitoring terminal at a 3GPP network layer in a home public land mobile network (HPLMN), a code word broadcast by a first terminal, wherein the code word is allocated to the first terminal by a first ProSe entity, and the first ProSe entity is a ProSe entity in the HPLMN; sending, by the monitoring terminal at the 3GPP network layer in the HPLMN, a first message to a receiving ProSe entity when the code word matches a prestored code word, wherein the first message carries the code word and a first application identity, the first application identity is an application identity of a first application, and the receiving ProSe entity is a ProSe entity in an HPLMN of the monitoring terminal; receiving, by the monitoring terminal at the 3GPP network layer in the HPLMN, a second message sent by the receiving ProSe entity, wherein the second message carries a application user identity, the v identity is an application user identity that is allocated to a first application user by a first application server, the first application user is a user of the first application of the first terminal, and the first application server is an application server of the first application; and discovering, by the monitoring terminal at the 3GPP network layer in the HPLMN, the first application user according to the application user identity, wherein the second message further carries the first application identity, and the first application identity is configured to indicate the first application corresponding to the application user identity.
10. A proximity service (ProSe) information transmission method, comprising: acquiring, by a monitoring terminal at a 3GPP network layer in a home public land mobile network (HPLMN), a code word broadcast by a first terminal, wherein the code word is allocated to the first terminal by a first ProSe entity, and the first ProSe entity is a ProSe entity in the HPLMN; sending, by the monitoring terminal at the 3GPP network layer in the HPLMN, a first message to a receiving ProSe entity when the code word matches a prestored code word, wherein the first message carries the code word and a first application identity, the first application identity is an application identity of a first application, and the receiving ProSe entity is a ProSe entity in an HPLMN of the monitoring terminal; receiving, by the monitoring terminal at the 3GPP network layer in the HPLMN, a second message sent by the receiving ProSe entity, wherein the second message carries a application user identity, the v identity is an application user identity that is allocated to a first application user by a first application server, the first application user is a user of the first application of the first terminal, and the first application server is an application server of the first application; and discovering, by the monitoring terminal at the 3GPP network layer in the HPLMN, the first application user according to the application user identity, wherein the second message further carries the first application identity, and the first application identity is configured to indicate the first application corresponding to the application user identity. 12. The method according to claim 10 , when the code word matches the prestored code word, and before the acquiring, by a monitoring terminal, a code word broadcast by a first terminal, further comprising: sending, by the monitoring terminal, a third message to the receiving ProSe entity, wherein the third message carries first information, a fourth identity, and the first application identity, wherein the first information comprises a third identity or a sixth identity, the third identity is a temporary terminal identity that is allocated to the monitoring terminal by the receiving ProSe entity, the sixth identity is a terminal identity of the monitoring terminal, the fourth identity is a temporary application user identity that is allocated to a second application user by the first application server, and the second application user is a user of the first application of the monitoring terminal; and receiving, by the monitoring terminal, a fourth message sent by the receiving ProSe entity, wherein the fourth message carries the code word.