In order to develop a new sort of thermally sensitive phosphor coating, the emission spectrum thermally sensitivity of Mg4FGeO6∶Mn induced by laser was studied. The spectrum measurement system with heating function was set up, and the emission spectrum of Mg4FGeO6∶Mn at various temperatures were measured. Absorption spectrum was measured, and the mechanism of formation of the structure of double peak was analyzed with the perturbation theory of crystal lattice. The group of peaks around 630 nm is represented by the transitions 4F″2 to 4A2, whereas the group of peaks around 660 nm is due to the transitions 4F′2 to 4A2. The occupancy of both excited states 4F′2 and 4F″2 is in thermal equilibrium. Thus increasing temperature causes the intensity of the emission in the group around 630 nm to increase at the expense of the emission intensity of the group around 660 nm. The various spectral regions in emission differ with temperature, which could be used to support the intensity-ratio measurement method. The intensity-ratio change curve as a function of temperature was fitted, which shows that the range of temperature measurement is between room temperature and 800 K.