Testing system of selective dual mode type for fuel cell stacks or vapor/carbon dioxide co-electrolysis stacks

A testing system of selective dual mode type for fuel cell stacks or vapor/COco-electrolysis stacks includes at least one testing structure, a reactant gas supply device, a vapor supply device, a power supply device, a power load device and a control-analyzing device. The power supply device and the power load device are connected to electrodes of the testing structure, and also connected to the control-analyzing device. When the testing structure is served for a fuel cell stack testing, the reactant gas supply device provides reactant gas into the testing structure, and a current generated by the fuel cell enters the power load device. When the testing structure is served for an electrolysis stack testing, the vapor supply device provides electrolysis vapor into the testing structure, and the power supply device exposes voltage on the electrodes.