This study investigated the thermal compression deformability of the low-alloyed Mg-Zn-Y-Zr magnesium alloy temperatures ranging from 300 to 450 °C, and strain rates between 0.01 s⁻¹ and 1 s⁻¹. A hot processing map was established using a novel constitutive model. The results demonstrate that the flow stress of the low-alloyed Mg-Zn-Y-Zr alloy is markedly affected by the deformation temperature and strain rate, predominantly manifesting characteristics of work hardening (WH) and dynamic recrystallization-induced softening. The high-temperature rheological behavior of the alloy is accurately portrayed with a constitutive model, with an activation energy measured at 287 kJ/mol. The mechanism of dynamic recrystallization (DRX) gradually shifts from twinning dynamic recrystallization (TDRX) to continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX). At 400 °C, as the strain rate decreases, the I-phase in the microstructure gradually transforms into the W-phase, weakening the inhibitory effect on DRX grain growth.