In order to investigate the kinetic mechanism of thermal decomposition of poplar sawdust, the thermogravimetric experiments were performed using a thermogravimetric analyzer. The results showed that the activation energy varied from 17.64 kJ/mol to 161.14 kJ/mol. The pre-exponential factor values indicated empirical first-order reaction. The Gibbs free energy values varied from 127.88 kJ/mol to 223.55 kJ/mol, and the entropy changes were negative. The calorific value of the biomass was 19,482 kJ/kg.