The Copolymer (p-HBTF) was synthesized by condensat ion of p-hydroxybenzoic acid and thiosemicarbazide with formaldehyde in the presence of 2M HCL as a catalys t at 126 ± 2 0 C for 5 hrs. with molar proportion of reactants. The copolymer (p-HBTF) was characterized by element al analysis, FT-IR, UV-Visible 1 H-NMR Spectroscopy. The thermal decomposition behavior of copolymer was stu died by using TGA in static nitrogen atmosphere at a heating rate of 10 0 C/min. Freeman Carroll and Sharp-Wentworth methods were used to calculate the thermal activation energy (Ea), the order of reaction (n), entropy Cha nge ( ∆ S), free energy change ( ∆ F), apperent entropy change ( ∆ S), and frequency factor (Z). The thermal activatio n energy determined with the help of these method was in good agreement with each other. The copolymer possesses antimicrobial activity for certain bacteria such as S. subtilis, , E.coli, S. typhi .