The invention discloses a method for acquiring a WLAN authentication and privacy infrastructure certificate, comprising the steps as follows: a terminal sends a certificate issuing request to an authentication server; and the authentication server searches the WAPI certificate of a user according to the account of the user of the terminal carried in the received certificate issuing request and sends the found WAPI certificate to the terminal. In the invention, before carrying out the first certificate authentication, the terminal is accessed to the IMS network by 3G RAN, and acquires the WAPIcertificate by the signaling interaction between the IMS network and the authentication server; the invention avoids the inconvenience of the user in acquiring the certificate by an off-line mode andsimplifies the certificate management process of the users and operators and the process that the terminal acquires the certificate by running background, thereby improving the user experience.