A high-sensitivity high-temperature sensor based on dislocation welding of suspended optical fiber is provided and includes a broadband light source, an optical fiber circulator, a sensing head and a spectrometer. The optical fiber circulator is connected to the broadband light source, the sensing head and the spectrometer individually, the sensing head includes a first single-mode optical fiber, a multi-mode optical fiber, a suspended core optical fiber and a second single-mode optical fiber which are connected in sequence. The high-sensitivity high-temperature sensor has the following advantages: simple to manufacture, no need for expensive special equipment; small sizes, compact structure, easy to use; full optical fiber structure, which can measure high temperatures up to 1000 degrees; no need for adhesive, good sensor stability; double cavities in parallel can generate vernier effects with high sensitivity.