Fire poses a great threat to people's production and life, but existing fire sensors have limitations in installation space, measurement range and applicable environment. Therefore, it is necessary to develop new types of fire sensors. This paper designs and implements an industrial fire warning optical fiber sensor that is reliably encapsulated by a stainless steel capillary tube. This paper greatly improves the high temperature resistance of traditional fiber grating sensors through high temperature regeneration processing of fiber gratings. Experiments on the prepared sensor show that the sensor can measure temperature up to 1000 ℃, linearity is 0.99951, and the response time of 90% signal at 1000 ℃ is less than 3 s, it is suitable for fire warning.