Abstract: Disclosed are a method and a device for determining the maximum gear ratio of a transmission. The method comprises: on the basis of universal characteristic data of an engine, determining corresponding minimum engine fuel consumption rates when a vehicle is travelling at multiple constant speeds, and engine rotation speeds corresponding to the minimum engine fuel consumption rates; for each of the minimum engine fuel consumption rates, determining a speed ratio corresponding to the minimum engine fuel consumption rate; obtaining a weighted average of the corresponding engine fuel consumption rates when the vehicle when travelling at the various constant speeds under each speed ratio; and determining the speed ratio, corresponding to the minimum from among the obtained weighted averages of the engine fuel consumption rates, to be the maximum gear ratio of a transmission. The method obtains the maximum gear ratio of the transmission based on the consideration of fuel economy.