To measure the temperature range from room temperature to 1 000℃, a sapphire-ruby fiber -based multi-probe thermometer was proposed. The thermometer system combines fluorescence lifetime with radiationand, which can measure the temperature of 8 probes at the same time. A digital iteration algorithm based on area balance was presented to measure the fluorescence lifetime. Compared with the Fast Fourier Transformation algorithm through simulation, the proposed algorithm features robust, high efficiency, strong anti-noise and immune to background level. The temperature test and stability test of the system were studied for a long time, the results show that the system has high stability and accuracy, the measured temperature range from room temperature to 1 000℃, the accuracy can be ±1℃.