A method and a broadband device for modem dial-up terminal which relate the communication with an evolved high rate packet data (eHRPD) network by using an existing protocol by receiving, by a broadband device, a first link control protocol (LCP) request message of a wireless network side device; processing an extensible authentication protocol (EAP) authentication field of the first LCP request message into an authentication field supported by a dial-up terminal; sending the processed first LCP request message to the dial-up terminal; receiving a first LCP response message returned by the dial-up terminal; processing an authentication field of the first LCP response message into an authentication field supported by the wireless network side device; sending the processed first LCP response message to the wireless network side device; and acquiring an Internet Protocol (IP) address from the wireless network side device, and sending the IP address to the dial-up terminal.