Proton Exchange Membrane Fuel Cell (PEMFC) has being widely applied in electric vehicle and distributed generation for its low corrosion, low-temperature operation and environment friendship. It should be concerned over the control and maintenance of its auxiliary equipments, placement site, restoring of hydrogen and other things when physical PEMFC is used. However, PEMFC’s volt-ampere (V-I) external characteristics draw our more attention rather than its ontology or peripheral devices control which keeps PEMFC working properly in many appliance studies. So, there is another solution to introduce power electronic technique to construct a FC power electronic simulator which simulates FC’s external characteristic including static and dynamic states and keeps away those troubles mentioned above. A buck converter is adopted to construct the FC simulator. The test DC current source load is acquired by a buck converter which main circuit is similar to the FC simulator. The experiments show the FC simulator has done a good job to simulator FC’s volt-ampere external characteristic and it is cost saved.