A communication method and a communications apparatus in which the method includes: a terminal device receiving a first authentication request from a security function network element, and obtaining authentication reference information based on the first authentication request, where the authentication reference information is a response value, a resynchronization token, or a cause indication value. The terminal device sends an authentication response message to the security function network element, where the authentication response message includes a first information element used to carry the response value, a second information element used to carry the resynchronization token, and a third information element used to carry the cause indication value, and the authentication reference information is carried in an information element corresponding to the authentication reference information.