Abstract: The disclosure proposes a routing gateway selecting method, a controller and a vehicles network system. The method is adapted to a controller disposed on a fleet of vehicles configured by a plurality of vehicles, and the controller is configured to select a routing gateway among a plurality of gateways for routing an access point (AP). The routing gateway selecting method includes: predicting a bandwidth of each of the gateways; calculating a transmission cost of each of the gateways based on a load condition and the bandwidth of each of the gateways and a hop count between each of the gateways and the AP; and selecting the routing gateway among the gateways for routing the AP according to the transmission cost of each of the gateways.