A network authentication, authorization and accounting system and a method thereof, wherein said system comprises: a subscriber device, via which a subscriber is connected with the network; an access server, connected with the subscriber device and designed to enable the subscriber device to access the network; an AAA server, connected with the access server and designed to collaborate with the access server to accomplish authentication, authorization, and accounting for the subscriber accessing the network; a service server, connected with the access server, designed to provide specific services, to exchange authentication and authorization information with the AAA server, and to interact with the subscriber device to provide the service; a service accounting server, connected with the service server, designed to collaborate with the service server to accomplish accounting for service resource use of the subscriber, and to send the accounting data to the AAA server. Accordingly, the present invention also discloses a network authentication, authorization and accounting method. The present invention enables a subscriber to access different types of services with only the subscriber identification information (user name and password) through a single identity authentication process, and supports centralized accounting.