A high temperature sensor based on an ultra-abrupt tapered fiber Michelson interferometer fabricated by the fusion-splicing method is proposed. The sensor consists of a single abrupt taper and the cleaved surface is used as the reflection mirror. The thermal characteristic is investigated at 25 to 1 000 oC. The sensitivity of the sensor is observed to vary with the temperature, that is, 25 and 78 pm/ C at 25–300 and 300–1 000 oC, respectively. The Michelson interferometer sensors have the advantages of simple structure, cost effectiveness, compactness, and simple fabrication process.