In order to quantitatively study the metamorphism of coal, by calculating the changes of reflectivity with time and temperature and the changes of temperature with time and reflectivity, the results show that the temperature time reflectivity ternary coal metamorphism thermodynamic equation (Cmte) proposed by Mr. Wu Chonglong is feasible. Although it is only an empirical formula, the mathematical formula is more convenient and accurate than the diagram, The critical temperature of lignite is

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... 3°C and that of long flame coal is 56.9°C. The empirical formula of temperature time reflectance is demonstrated to explain the metamorphism of coal. By compiling temperature reflection (time) maps of middle coal formation in Carboniferous, Jurassic and Cretaceous, this paper explains the concept of "the longer the thermal time, the higher the degree of metamorphism" with isothermal horizontal line or equal reflection vertical line. The temperature and effective metamorphic time in the literature of Nantong coalfield in Sichuan further prove the accuracy and practicability of Cmte. The mathematical formula of temperature time reflectance can not only know the cross verification temperature of time and reflectance, but also know the time with a difference of less than 1.4% from the original effective metamorphic time. It is proved that the empirical formula of temperature time reflectance can explain the metamorphism of coal.