Bruch [3] observed very significantly different activation nergies of sintering for the compacts with different green densities. Young and Cutler concluded that nonisothermal sintering could not be used to identify the mechanism of diffusion because of the wide variation of the evaluatedactivation energies. Although they [4] pointed out that the particle size distribution may be a factor affecting the evaluation of the activation energy, the true reason for the variation in evaluating the activation energy of sintering is still not realized. The present investigation is to explore the reasons for the variation in evaluating activation energies of sintering.