The thermal decomposition of Tb2(O-MBA)6(PHEN)2 (O-MBA: o-methylbenzoate; PHEN: 1,10-phenanthroline)and its kinetics were studied under the non-isothermal condition by thermogravimetry-derivafive thermogravimetry (TG-DTG) techniques. Kinetic parameters were obtained from analysis of TG-DTG curves by the Achar method and the Madhusudanan-Krishnan-Ninan (MKN) method. The most probable mechanism function was suggested by comparing the kinetic parameters. The kinetic equation for the first stage can be expressed as dα/dt = Aexp(-E/RT) @ 3(1 - α)2/3. The lifetime equation at mass loss of 10% was deduced as lnτ= -28.7429 + 19797.795/T by isothermal thermogravimetric analysis.