In order to elaborate a simple method for the comparison of catalyst activity in the reactions of thermal decomposition of glycerol, thermogravimetric analysis (TGA) of glycerol and its mixtures with catalysts Pt/C and Pd/Al2O3, supports of catalysts and sand were conducted at different heating rates under nitrogen atmosphere. TGA and TGA – FTIR analysis showed that under the experimental conditions the evaporation of glycerol influenced the shape of the mass loss curve more than the decomposition. By the use of temperature profile: ramping to the isotherm 100 OC at heating rate 50 OC/min, 5 min for soak segment and linear heating in the temperature range 100 – 350 OC at the heating rate 50 OC/min the water evaporation stage is excluded and the mass loss curve is relative simple with a characteristic peak of the derivative curve (DTG). The DTG peak values are not influenced by sand and supports of catalysts, but linear dependent on the catalyst/glycerol mass ratio. The slope of this linear correlation for 5% Pt/C is twice larger than the slope of linear correlation for 3,19% Pd/Al2O3, from where we concluded that the investigated platinum catalyst is twice more active in the thermal decomposition reaction of glycerol than the investigated palladium catalyst.