A device, a system, and a method for automatically configuring application terminals in a home network are disclosed. The method is as follows. A home gateway receives identifier information of an application terminal sent by the application terminal through a Dynamic Host Configuration Protocol (DHCP). The identifier information of the application terminal is sent to a public network through a DHCP message, so as to determine a DHCP server corresponding to an automatic configuration server (ACS) of the application terminal. Address information of the ACS of the application terminal is obtained from the DHCP server on the public network through a DHCP message. The address information is transmitted to the application terminal, so that the application terminal obtains configuration information from the ACS according to the address information to perform an auto-configuration. Thus, a problem that the application terminal in a home network cannot directly obtain an ACS Universal Resource Locator (URL) through a DHCP message is solved, so that an auto-configuration of the application terminal is realized.