Through a semiexperimental dynamic modeling of a direct methanol fuel cell (DMFC) system, transient behaviors on describing cell temperature, methanol crossover, water crossover, and electric power are presented. By different operating manners, the new input determinations are addressed. To investigate the performance of DMFC systems, the presented fuel and exergetic efficiencies for the specific probe of energy utilization are evaluated. Through both steady-state and unsteady state analyses, the manipulation of cathode pressure and anode inlet flow temperature is a feasible approach for temperature regulation, but methanol crossover is restricted.