Composite electrolytes were prepared by doping carbonates (Li₂CO₃ 53 mol% and NaCO₃ 47mol%) with different mass fractions (10%, 20%, 30%) into electrolyte (GDC). The electrochemical properties of the composite electrolyte were characterized by conductivity test and scanning electron microscopy (SEM). Anode powder was prepared by doping composite electrolytes into NiO, and the cathode powder was obtained by compounding the composite electrolytes with Li-treated NiO.The anode, cathode and electrolyte prepared above were pressed by dry pressure method to obtain a single cell supported by the anode.  The performance of the cell was characterized later. The results of electrochemical performance of single cell show that GDC with 30% carbonate has the highest power density, which is 1400 mWcm^-2 at 600 C.