A system for automatic security authentication in a wireless network includes a server and a terminal. The terminal includes a processor, a first communications unit, and a second communications unit. The server includes a database, a control unit, and a third communications unit. The processor receives an identification code of an access point through the first communications unit, and sends a message to the control unit through the second communications unit. The message includes the identification code of the access point, a user account and a user password. The control unit sends an authentication code corresponding to the identification code according to data stored in the database to the processor through the third communications unit. After receipt of the authentication code, the processor automatically logs in to the access point through the first communications unit to activate a wireless network access function.