Metal　oxides　have　been　applied　in　gas　sensor　technology　while　suffering　poor　sensitivity　and　high　working　temperature.　In　this　work,　a　novel　method　has　been　adopted　to　improve　these　problems　of　the　sensors.　A　mixture　of　Fe3+,　La3+,　Co2+　(Fe3+:　La3+　:　Co2+　=10:3:1)　and　dispersing　agent　in　water　solution　was　precipitated　by　adding　NH4+(pH=9)　under　agitation.　The　precipitate　was　filtered,　washed　and　drying,　then　immersed　with　0.5M　(NH4)(2)SO4　in　12hr.　Superacid　SO42-/LaCoFeO4　was　prepared　after　calcined　at　673K　for　1h.　The　thick　film　units　for　oxygen　sensor　were　dintered　at　673K　for　3h.　The　structure　of　this　catalyst　has　been　characterized　by　means　of　powder　X-ray　diffraction　(XRD),　transmission　electron　microscope　(TEM),　IR,　X-ray　photoelectron　spectroscopy　(XPS)　and　specific　surface　area　measurements.　The　result　indicated　that　the　SO42-/LaCoFeO4　grain　sizes　(＜=　10nm)　were　smaller　and　the　specific　surface　area　(126M(2)/g)　was　higher　than　the　pure　metal　oxide　LaCoFeO4.　The　acid　strength　was　measured　by　the　model　reaction　of　ethyl　acetate　synthesis　and　attributed　as　superacid.　In　addition,　the　SO42-　was　combined　with　metal　ions　in　a　bidentate　fashion.　The　binding　energy　of　SO42-/LaCoFeO4　was　larger　than　that　of　LaCoFeO4.　The　sensitivity　as　well　as　the　working　temperature　is　improved　by　comparison　with　the　pure　LaCoFeO4　phase.　The　relationship　between　the　oxygen　sensing　properties　and　structure　has　also　been　discussed.