The combustion kinetic characteristics of wood powder and pellet were investigated within thermogravimetric analyser (TGA) and tube furnace system. The kinetic parameters of these two different forms of woody fuel were measured and derived by double-step-and-double-equal and isothermal method, respectively. The results showed that the combustion mechanisms of wood powder kept consistent through the whole process, while the combustion mechanisms of wood pellet differed significantly between the volatile and char combustion stages. The most probable mechanism functions of the two different forms of woody fuel were not the same due to the differences in internal heat and mass transfer properties. In addition, activation energy values varied from 92.33 kJ·mol−1 for wood powder to 71.20 kJ·mol−1 for wood pellet, while the preexponential factor value of wood powder (2.55×108 s−1) was far greater than the one of the wood pellet (78.55 s−1) by seven orders of magnitude.