A smart home system using a portable device in which a gateway function is installed in the portable device to provide a smart home service using a multiplex gateway, and a control method thereof is provided. The smart home system includes one or more portable devices and one or more home appliances located in a home, each of the one or more portable devices and one or more home appliances having a gateway, a home network to interconnect the one or more portable devices and the one or more home appliances, and a master device selected from among the one or more portable devices or the one or more home appliances, the master device activating the gateway thereof to connect the home network with an external communication network, wherein the master device transfers a home appliance control command to a corresponding one of the one or more home appliances.