Abstract: The present invention is a power output control system for electric vehicle with hybrid fuel cell, which is an optimal design of DC/DC converter and applies the controller area network (CAN) as a connected instrument for communication to make a power source tend to be more flexible. When the invention is designed in the states of medium and low loads (for example, cruise in constant speed), the main electric energy supplied by the fuel cell boosts the fuel cell to an appropriate voltage through the control of DC/DC converter. While in the state of high load (for example, transient acceleration or uphill creep), the fuel cell may be served as an on-board charger. Not only the fuel cell may provide a maximum base load of electric power, but also the remaining requirement of electric energy is matched with the additional output of electric energy supplied by a high power secondary battery.