The high temperature and destructive power, made it difficult to test the explosion temperature of thermo-baric explosive. To effectively assess heat damage effect of thermo-baric explosive, multi-spectral high temperature measurement system is applied to transient high temperature test of thermo-baric explosive. The emissivity and the true temperature of explosion flame are calculated by using the secondary measurement method. In the data acquisition system, the test instrument achieves data collection and transmission 500 meters away in combination with optical fiber sensing technology and under the precondition to guarantee the participants safety. The measurement results show that the designed measurement system has the advantages of simple operation, high safety and better application prospect.