A system to measure transient temperature distribution on the brake disc rotor at high speed braking has been developed and its measuring principle and configuration were discussed in this paper. This system consists of two revolution sensors and two sets of optical fiber array, photoelectric elements, and microprocessor, which fiber array is so arranged that it faces the brake disc rotor. This new system has the following features: (1) Measuring is made using a visible radiation wavelength range for red hot temperatures higher than 550°C. The optical plastic fibers allow non-contact measuring In a narrow space. (2) Ever-changing temperature distribution patterns on the disc rotor surface during high speed braking can be measured for each revolution while the disc is revolving. (3) This system is less influenced by the variation in emissivity, thus providing stable characteristics. (4) Simultaneous measurings on the both friction surfaces of the disc rotor are possible. (5) Use of the magnetic bubble memory allows high speed data output while the memory device is compactly constructed. In addition, data output is available at any time as needs.