Abstract: A prepaid accounting system for a wireless local area network (WLAN) and a method thereof are provided. The system includes: an authentication control point, an authentication server, and a service control point. The authentication control point is used to control access of a subscriber to WLAN; the authentication server is used to perform authentication, authorization and accounting for the subscriber; and the service control point is used to store and update subscriber information. The method includes the steps of: upon the start of accounting, an authentication server requesting a service control point to check account balance of a subscriber; during the accounting, the authentication server periodically requesting the service control point to check the account balance of the subscriber; and upon the termination of accounting, the authentication server notifying the service control point of the termination of accounting and the service control point updating the balance.