A fleet maintenance method for generating a suggested speed for each vehicle in a fleet to maintain the vehicle in the fleet is provided. In the fleet maintenance method, vehicles are clustered into a plurality of sub-fleets, and in each sub-fleet, one vehicle is selected as a leader vehicle and the other vehicles are considered as member vehicles. Besides, a position coordinate and a speed of each vehicle in each sub-fleet are obtained, and the position coordinate is converted into a corresponding linear coordinate. In addition, a sub-fleet gravity center of each sub-fleet and a fleet gravity center of the entire fleet are calculated according to the linear coordinates. Moreover, a suggested speed of each leader vehicle is generated according to a gravity center distance of the leader vehicle, and a suggested speed of each member vehicle is generated.