<p>The kinetic energy of the ejected fragments is an effective index for quantitatively evaluating the failure severity of rockburst. To improve the measurement accuracy of the kinetic energy, the total kinetic energy was divided into translational and rotational kinetic energy in this paper. An analysis method for translational and rotational kinetic energy was subsequently proposed by introducing a four-eye high-speed photography system. Moreover, the true triaxial rockburst experiments on granite samples after heat treatment at various temperatures were carried out to reveal the evolution characteristics of the kinetic energy of rockburst. The experimental results reveal that with increasing the particle size of the rockburst fragment, the correction coefficient of measurement error of the translational kinetic energy increases first but then decreases. A power function law is obtained between the ratio of the rotational kinetic energy to the translational kinetic energy and the particle size of the rockburst fragment. Compared to the uncorrected kinetic energy measured by the system, the total kinetic energy presents a decreasing trend. The maximum proportion of total kinetic energy to uncorrected kinetic energy is 0.9. The peak stress, failure intensity and total kinetic energy all initially increase but subsequently decrease as the heat treatment temperature increases. The research outcome is favourable to revealing the impact of initial thermal damage on the rockburst mechanism.</p>