A study has been made of the kinetics of oxidation of mesophase pitch fibre by atmospheric oxygen under conditions of a steady rise in temperature and with isothermal holding. It has been shown that the rate of increase in the weight of the fibre through oxygen absorption by the latter obeys a first-order equation. The rate constant of oxidation at constant temperature and the parameters of the Arrhenius equation with the temperature rising at different rates have been found. It has been shown that these parameters are not dependent on the rate of increase in temperature, while the rate constant determined under isothermal conditions is similar to that calculated by the Arrhenius equation.