Thermal degradation behavior of rice straw fibers under isothermal heating conditions was studied. The data were modeled by considering the fiber as one pseudo-component using the Ma´ lek method. The kinetic model with reaction order n > 1 [i.e., RO(n > 1) = (1 - α)n] described the degradation process of rice straw fiber fairly well in a temperature range up to about 265 ℃. The kinetic parameters used include activation energy of 116 ± 5 kJ/mol, reaction order of 3.0 ± 0.2, and logarithmic value of preexponential factor [ln A] of 18.7 ± 0.1 ln s^(-1). The model obtained can be used to aid the development of straw fiber-engineering plastic composites.