The fracture of solids is accompanied by such physical and chemical phenomena as emissions of electrons, ions, photons and molecular particles. The understanding of the mechanisms of all these processes is impossible without the knowledge of the uvenil fracture surface (UFS) temperature. In this research the temperature of UFS of glassy polymer polymethylmethacrylate (PMMA) was measured in time range 10-60 mu s after the specimen rupture. The emissional infrared (IR) spectroscopy was chosen as an investigation method, that allows to obtain the Planck spectrum of the heat irradiation of the object, and by position of the maximum (lambda(max)) on the spectral curve with the application of Wien law (lambda(max) T = 2896 mu m .) to determine the radiating zone temperature of the progressing crack and of the UFS. It was shown that the IR emission spectrum contains two main components: the Planck (or ＇＇heat＇＇) component and the characteristic (or luminescent) one. The UFS warming-up of the PMMA does not exceed 200 degrees C. The temperature field in the vicinity of the top of the running crack and UFS of PMMA was calculated with the help of Rosenthal-Weichert-Schonert theoretical model. The kinetics of UFS cooling of PMMA, wich is in a good agreement with the experimental one in long time (tens of mu s) has been obtained. In the range of short time (smaller than 10 mu s) the experimental data are absent while the calculation given the value of maximum warming-up in the same time range (on the top of the running crack) similar to 250 degrees C.