This study investigates a roof separation sensor based on fiber Bragg grating. Simple structure, easy installation, and low cost are the advantages of this fiber optic sensor. This sensor does not exhibit charged characteristics, and it is suitable for coal mine applications. The sensor consists of mechanical structures and shifts the displacement of a wire rope through the rotation of multiple mechanical structures. Thus, it is convenient to use the wire rope to connect to the roof separation and vary the range and sensitivity. The sensor has three fiber gratings, which not only satisfies the requirements for monitoring multiple points but also provides a method for eliminating the temperature effects. The experimental results verify the reliable linearity of the sensor at multiple temperatures, and the accuracy can reach ±2 mm with a range of up to 300 mm.