The present invention refers to a test system for multi fuel high-temperature operating fuel cells, which allows the direct use of carbon-base fuels, including anhydrous ones, without promoting or limiting carbon deposition in the gas inlet and outlet ducts, as well as in the flow channels anode, said system comprising: a furnace (5) containing a reactor (4), the reactor consisting of at least two interconnection plates and at least one fuel cell (15) located between two interconnection plates, wherein one of the interconnection plates in contact with a fuel cell is a cathodic side, which receives oxidizing gas, and the other interconnecting plate in contact with said fuel cell is an anodic side, which receives combustible gas, the system further comprising a controlled means of gas feeding and exhaustion connected to the reactor (4), wherein each plate further comprises a plurality of flow channels (14) on its upper and lower surface, wherein the oxidizing gas and the combustible gas pass through the flow channels (14) to contact with the electrodes of the fuel cell (15), and wherein the base, top and interconnection plates are made of a zirconium oxide or cerium oxide-based material doped with one or more of the oxides of yttria, scandia, calcia, gadolinia, samaria, alumina and cobaltite, with a total amount of dopants up to 20% by weight.