A　novel　mixed　ionic　composite　electrolyte　powder　of　BaCe　0.8Y　0.2O　3-δ　-Ce　0.8Gd　0.2O　1.9　(BCY-GDC　in　a　molar　ratio　n　(BCY):n　(GDC)　=　1:1)　was　synthesized　via　a　two-step　gel　combustion　method.　The　properties　of　BCY-GDC　electrolyte　sintered　at　different　temperatures　and　the　electrical　performance　of　single　cell　with　BCY-GDC　electrolyte　were　investigated.　The　homogeneous　BCY-GDC　composite　powder　with　the　average　particle　size　of　40　nm　was　synthesized.　The　relative　density　and　conductivity　of　BCY-GDC　pellet　increased　with　increasing　sintering　temperature.　The　dense　pellets　with　the　BCY　and　GDC　phases　were　obtained　at　the　sintering　temperatures　of　1450°C.　The　single　cell　with　BCY-GDC　composite　electrolyte　had　an　open　circuit　voltage　of　0.95　V　at　450°C　and　a　peak　power　density　of　0.4　W/cm　2　at　700°C.