The particle overheating is an important problem in the industrial catalytic gas-phase olefin polymerization reactors. It has been first investigated with a pseudo-stationary model of a single polymer particle by Hutchinson and Ray (J. Appl. Poly. Sci. 34 (1987) 657). A systematic study of overheating of polymer particle with models based on Fick's and dusty gas model (DGM) transport described below is conducted by tools of continuation (steady-state) analysis and by dynamic simulations. The consideration of convective flow of species in particle pores driven by pressure gradient due to the change in the number of moles in the course of the polymerization reaction makes the polymer particle in the reaction environment containing only monomer more susceptible to overheating. It is found that an intraparticle mass transport resistance has an important effect on particle overheating. The prediction and discussion of a time-scale of particle overheating under industrial process conditions is coupled with the discussion of the dynamics of particle growth and dynamic changes of catalyst activity.