Abstract: A method for easily determining the specifications of a fuel cell and a capacitor constituting a fuel cell power generation system according to an operational mode of an electric load connected to the fuel cell power generation system. The specifications of the fuel cell and the capacitor connected in parallel to the fuel cell are determined by a first step for determining a limit value di/dt_lmt of an increasing rate di/dt of an output current density per unit cell area of the fuel cell according to at least an operational mode of the electric load connected to the fuel cell system, a second step for determining an internal resistance Rfc of the fuel cell on the basis of a current-voltage (I-V) characteristic of the fuel cell based on the di/dt_lmt determined by the first step, and a third step for determining the internal resistance Rcap of the capacitor such that a characteristic value K calculated by weighted multiplication of Rfc determined by the second step and Rcap lies within the range of 0.