This application provides a data integrity protection method and apparatus. A terminal device obtains an integrity protection algorithm and a key corresponding to a session, and a DRB corresponding to the session, and performs, by using the integrity protection algorithm and the key corresponding to the session, integrity protection on data of the DRB corresponding to the session; or a terminal device obtains an integrity protection algorithm and a key corresponding to a flow, and a DRB corresponding to the flow, and performs, by using the integrity protection algorithm and the key corresponding to the flow, integrity protection on data of the DRB corresponding to the flow, where one session includes a plurality of flows, different integrity protection algorithms and keys can be used for different sessions, and different integrity protection algorithms and keys can also be used for different flows. In this way, integrity protection is more flexible and meets security requirements of a same user for different services.