A compact fiber Fabry-Perot interferometer (FPI) sensor for high temperature measurements is proposed and demonstrated. The FPI consists of a small core microstructured fiber and single mode fiber, and it is enabled by partial Fresnel reflection at the interface of the two fibers and the end surface Fresnel reflection of the microstructured fiber. Simple splicing and cleaving techniques are used to construct such an interferometer, and the fringe contrast can reach 20 dB. Response to high temperature up to 1000°C is tested and a sensitivity of 17.7 pm/°C at 1570 nm is obtained. This proposed sensor is compact, and fabricated only with splicing and cleaving techniques, which shows a great potential for space-limited high temperature sensing applications.