A network system includes a plurality of network groups. Each of the network groups includes at least one node. The at least one node is configured for transmitting a beacon response according to a beacon request transmitted by a new node. When the at least one node of the at least one of the network groups transmits the beacon response, at least another one of the network groups is in a sleep state, and the new node connects with the at least one node of the at least one of the network groups according to the beacon response. A connection method of the network system is also disclosed herein.