NOVELTY - Low carbon hydrocarbon and carbon dioxide conversion catalyst comprises a carrier, transition metal oxide and alkali metal oxide with mass ratio of 100:(8-20):(2-10). Preparation of the catalyst comprises molding carrier, drying and baking, dipping in transition metal and alkali metal containing soluble solution, drying and baking to obtains finished product catalyst. The carrier is silica, alumina, kaolin, bentonite, sepiolite, attapulgite, montmorillonite and/or diatomaceous earth. The transition metal oxide is iron, manganese or chromium oxide.    USE - The catalyst is useful for preparing ethane (claimed).    ADVANTAGE - The catalyst has good activity and high product selectivity. The method has easy operation and is suitable for industrial production.    DETAILED DESCRIPTION - Low carbon hydrocarbon and carbon dioxide conversion catalyst comprises a carrier, transition metal oxide and alkali metal oxide with mass ratio of 100:(8-20):(2-10). Preparation of the catalyst comprises molding carrier, drying and baking, dipping in transition metal and alkali metal containing soluble solution, drying and baking to obtains finished product catalyst. The carrier is silica, alumina, kaolin, bentonite, sepiolite, attapulgite, montmorillonite and/or diatomaceous earth. The transition metal oxide is iron, manganese or chromium oxide. The alkali metal oxide is alkali metal or alkaline earth metal oxide. INDEPENDENT CLAIMS are also included for:    (1) preparing the low carbon hydrocarbon and carbon dioxide conversion catalyst, comprising molding carrier, drying and baking at 500-620 degrees C for 2-5 hours,, dipping in transition metal and alkali metal containing soluble solution, drying and baking at 520-650 degrees C for 2-6 hours to obtains finished product catalyst; and    (2) use method of the low carbon hydrocarbon and carbon dioxide conversion catalyst for producing ethane, where the temperature is 600-820 degrees C, the pressure is 0.03-1.2 MPa, the raw material airspeed is 200-3000 hours, the low carbon hydrocarbon/carbon dioxide molecule ratio is 0.25-4, and the low carbon is ethane, propane, ethane rich gas, or propane rich gas.