Explosive flames have the characteristics of short duration and rapid temperature changes. Currently, the reported methods for measuring the temperature of explosion flames use colorimetric pyrometers and infrared thermal imagers. This type of research has a slow data collection speed. It cannot obtain the thermodynamic temperature (true temperature), which limits the practical application of temperature field measurement in explosion flames. Multispectral thermal imagers can achieve a wide range and high dynamic measurement of the true temperature field. However, there have been no reports on remote measurement of explosive flames based on multispectral thermal imagers. In response to this challenge, this article focuses on developing long-distance optical systems and constructing long-distance true temperature fields. The results show that the remote multispectral thermal imager can achieve a measurement speed of 100 kfps, and the uncertainty of true temperature measurement is 2.6%.