NOVELTY - A high temperature steam electrolysis and methane oxidation synchronizing method involves using three-layer yttria-stabilized zirconia (YSZ) homogeneous ceramic sheet as single supporting portions. Lanthanum-strontium-chromium-iron nanogranules are loaded on the ceramic sheet to build a cathode and an anode. The ceramic sheet is reacted and heat-processed. Silver wire fixed with electrically conductive adhesive is coated on anode and cathode and heat-treated. The electrolytic cell is subjected to methane oxidation and steam electrolysis. Hydrogen and carbon monoxide mixed fuel is obtained.    USE - Method for synchronizing high temperature steam electrolysis and methane oxidation that is utilized for producing fuel.    ADVANTAGE - The method enables synchronizing the high temperature steam electrolysis and methane oxidation in an inexpensive manner with high Faraday current efficiency of 100%, and is suitable for regenerative electric energy storage and reforming fields.    DETAILED DESCRIPTION - A high temperature steam electrolysis and methane oxidation synchronizing method involves using three-layer yttria-stabilized zirconia (YSZ) homogeneous ceramic sheet as single supporting portions. Middle layer of the three-layer YSZ homogeneous ceramic sheet is dense electrolyte with thickness of 200 microns. Porous YSZ layer with thickness of 50 microns is present on both sides of the YSZ ceramic sheet. The porous YSZ layer has porosity of 40%. Lanthanum-0.75-strontium-0.25-chromium-0.5-iron-0- delta nanogranules are loaded on two sides of YSZ homogenous ceramic sheet to build cathode and anode on both sides of the ceramic sheet. The ceramic sheet is reacted at 650 degrees C and heat-processed for 30 minutes to obtain solid oxide electrolytic unit cell. The electrolytic unit cell is heat-treated at 1100 degrees C for 3 hours. Silver wire fixed with electrically conductive adhesive is coated as current layers on the anode and cathode and heat-treated at 550 degrees C for 30 minutes. The heat-treated electrolytic cell is subjected to methane oxidation and steam electrolysis simultaneously. The composite cathode is passed into mixed atmosphere. Electrolytic voltage of 1.2-1. 8V is applied between composite anode and composite cathode at 700-800 degrees C for steam electrolysis. Methane gas is passed into composite anode for electrochemical oxidation. Hydrogen and carbon monoxide mixed fuel is obtained. The mixed atmosphere is 10 vol.% water vapor and remaining argon gas.