We present an optical fiber Fabry-Perot (F-P) temperature sensor based on metal welding technology. The fiber sensor is composed of a single-mode fiber and a metal capillary that are encapsulated by metal welding technology. The relationship between the cavity length and sensitivity is analyzed theoretically. The experimental results show that the sensitivity of the fabricated sensor reaches 3.85 nm / ° C when the F-P cavity length is 171 μm. In addition, the sensitivity of the F-P temperature sensor increases as the cavity length of the F-P temperature sensor decreases. The proposed sensor fabricated by metal welding technology has the advantages of a high sensitivity, simple fabrication, simple structure, and low cost.