The present invention relates to a system and method for controlling an integrated network of a vehicle, and more particularly, to a system and method, which separately identifies a malfunction of a plurality of communication networks applied to a vehicle and integrally controls power off and power on of the communication networks using a communication gateway. The integrated network system includes: a gateway configured to connect a plurality of networks; a plurality of vehicle networks connected to the gateway and connectable to each other by the gateway; and an Ethernet configured to transmit a signal processed in the gateway to the exterior of the gateway to analyze communication states of the plurality of vehicle networks connected to the gateway.