Microstructural evolution of commercial grade pure magnesium was studied during plastic deformation by torsion under high pressure at ambient temperature and by compression at temperatures ranging from 293 to 773 K and at a strain rate of 3×10⁻³ s⁻¹. Grain refinement takes place by operation of dynamic recrystallization (DRX) at all examined temperatures. The mechanisms of DRX change with temperature and strain. As a result, unusual dependencies of recrystallized grain size against strain and recrystallized volume fraction against temperature are observed. In the temperature interval of 293–623 K the deformation twinning results in “twin” mechanism of DRX, which processes strain softening at an initial stage of deformation. At T≤423 K the other mechanism of low temperature DRX takes place at high strains. Such DRX is accompanied by strain hardening. In contrast, continuous DRX (CDRX) yielding a steady-state flow operates frequently at temperatures ranging from 523 to 773 K . CDRX occurs mainly in overall recrystallization process at elevated temperatures. Discontinuous DRX (DDRX) takes place by bulging of boundaries of coarse recrystallized grains evolved from twins at T=723 K . DDRX occurs repetitively, but gives an insignificant contribution into total recrystallization process. The present results suggest that the mechanisms of DRX and the deformation mechanisms are closely related.