A smart home network system includes a number of traditional home devices having wireless communication function, a smart gateway, and a plurality of signal conversion devices. When the smart gateway wants to control a traditional home device, the smart gateway sends a cable control signal to a related signal conversion device in the area where the target traditional home device is placed. The related signal conversion device receives the cable control signals from the smart gateway, and converts the cabled control signal into a wireless control signal conforming to the wireless communication function type of the target tradition home device, then transmits the wireless control signal to the target traditional home device. Therefore, the traditional home devices with wireless communication function can be connected into the system, and be controlled by the smart gateway.