The invention relates to an oxide film thermocouple and a preparation method thereof. A magnetron sputtering technology is adopted, the oxide film thermocouple used for high temperature measurement is prepared on a high temperature ceramic substrate in a deposition manner; and an oxide protection layer is coated to improved the heat volatility of the oxide film thermocouple and improve the usage performance of the thermocouple. The film thermocouple is directly pasted to the surface of the ceramic substrate, can be used in a vacuum condition and an oxidation atmosphere and can work stably for a long time under a high temperature from 1000 DEG C to 1250 DEG C.