The invention relates to a card type broadband network access system and a method thereof. The system comprises a card reading terminal for authenticating subscriber terminals accessing the broadband network and forwarding DHCP requests of the subscriber terminals and IP addresses distributed to the subscriber terminals; a two-layer switch for forwarding the DHCP requests of the subscriber terminals and the IP addresses distributed to the subscriber terminals, and for uploading / downloading data information desired by the subscribers; a three-layer switch for distributing IP addresses to thesubscriber terminals. The method comprises steps of the carding reading terminal authenticating subscriber terminals accessing the broadband network, receiving the DHCP requests of the subscriber terminals after the authentication is passed; the two-layer switch receiving the DHCP requests forwarded by the two-layer switch and sending them to the three-layer switch; the three-layer switch distributing IP addresses to the subscriber terminals after receiving the DHCP requests; the subscriber terminals receiving the IP addresses through the two-layer switch and the card reading terminal.