A kind of multi-target multi-spectral thermometer has been developed to be used in large explosive environment. At the moment of explosion, the thermometer simultaneously collects explosion flame radiation energy under different spectra after the lights go through the prism spectrometer. The second measurment method was used to calculate true temperature and emissivity of the explosion flame. The fiber-optic long-distance transmission technique and fiber coupling technique were used for the first time in optical system design, which largely solves the problems of anti-vibration, anti-explosion and anti-electromagnetic interference for the core of the instrument. The high-speed acquisition system and multi-stage amplification system were used to realize instaneous collection of the rapidly changing explosion flame temperature. The wireless long-distance transmission was used to ensure the staff safety.