Schiff’s bases (4-((Furan-2-ylmethylene) amino) benzene sulfonamide (FMABS) and 4-((thiophen-2-ylmethylene) amino) benzene sulfonamide (TMABS)) were prepared from the condensation between 2-furaldehyde, 2-Thiophenecarboxaldehyde and 4-aminobenzene sulfonamide. These were characterized by microanalysis, FT-IR and NMR (1H and 13C) techniques. Thermal decomposition of FMABS and TMABS was studied by TG/DTG under dynamic oxygen atmosphere at different heating rates of 10, 15 and 20 K min-1 using under non-isothermal conditions and compounds were decomposed into two steps as evidenced from the DTG curve. The kinetic parameters were calculated using model-free and model-fitting methods. Einv and Ainv values are coincided with the average Ea values are determined by Friedman and KAS isoconversional methods. Each decomposition step is followed in different kinetic models, the thermal decomposition of FMABS was described by F2 and F1 models (stages I and II) and for TMABS, A3 and F2 models (stages I and II). Thermodynamic data clearly show that the decomposition processes are absorption of heat and non-spontaneous nature.