A method, an apparatus, and a system for acquiring a configuration file in a data over cable service are provided. The system includes: a convergence device, a cable modem terminal system CMTS assembly, and a cable modem CM, where the convergence device is connected to the CM using the CMTS assembly. The convergence device may be configured to intercept a first DHCP response message sent by a DHCP server to the CM; acquire configuration file information of the CM from the first DHCP response message; send the configuration file information of the CM to the CMTS assembly; replace address information of a Trivial File Transfer Protocol TFTP server in the first DHCP response message with address information of the convergence device, to form a second DHCP response message; and send the second DHCP response message to the CM.