Abstract: The present application provides an identity authentication method and a terminal device. In an example, a client on a terminal device acquires a user identifier (ID) and a password to be authenticated in response to an identity authentication operation from a user; the client acquires an additional password according to the user ID; and the client sends an identity authentication request to a server, where the identity authentication request includes the user ID, the password, and the additional password, so that the server is capable of performing identity authentication in response to the identity authentication request based on a user ID, a password, and an additional password stored on the server.