NOVELTY - The method involves calculating (F2) a fuel cell demand current based on calculated driver demand current. The target flow rate-1 of air to be supplied to a fuel cell stack is calculated (F6) based on fuel cell demand current and target stoichiometric ratio (SR) of air. The calculated target flow rate-1 is compensated (F8) using target SR to follow target SR of air. Revolution per minute (RPM) command value of air blower is calculated based on compensated target flow rate-2 and amount of air currently measured. Operation of air blower is controlled based on calculated RPM command value.    USE - Method for controlling fuel cell system of fuel cell vehicle and motor vehicle such as passenger automobiles including sports utility vehicles (SUV), bus, truck, and commercial vehicle, watercraft including boat and ship, aircraft, and hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen powered vehicles and gasoline-powered and electric-powered vehicles.    ADVANTAGE - The fuel cell system is controlled to supply an accurate amount of air to a fuel cell stack, so that flooding and dry-out which occurs in the fuel cell stack due to an excessive amount of air being supplied to the cathode can be prevented. The excessive supply of air that is unintended and unnecessary is minimized, so that unnecessary energy consumption for the operation of an air blower can be prevented. Thus, fuel efficiency of a fuel cell vehicle can be improved. The power performance of the fuel cell system is improved, so that generation of noise from an air blower during a transition period can be prevented.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a non-transitory computer readable medium storing computer program for controlling fuel cell system.    DESCRIPTION OF DRAWING(S) - The drawing shows a flowchart illustrating the method for controlling the supply of air and the fuel cell current.    Step for indicating current vehicle speed (F1)    Step for calculating driver demand current (F2)    Step for calculating air target flow rate-l based on the fuel cell demand current-2 and target stoichiometric ratio of air (F6)    Step for calculating stoichiometric ratio of air based on fuel cell current and air flow rate by controller (F7)    Step for compensating calculated target flow rate-1 using target SR to follow target stoichiometric ratio of air (F8)