The present invention is to provide a method for automatically configuring a gateway device through a mobile device, wherein the gateway device is installed with configuration software for connecting to a mobile device through a wireless communication unit thereof, and the mobile device is installed with automatic network connection software and configuration information. After activating the automatic network connection software, the mobile device reads the configuration information, searches for currently available wireless network device, establishes a peer-to-peer connection with the gateway device corresponding to the wireless network device whose Service Set Identifier (SSID) matches the SSID in the configuration information, and then activates the configuration software and sends the configuration information to the gateway device. Once the configuration software obtains the configuration information, a network connection configuration process of the gateway device is automatically completed.