Fine-grain Mg_(95.50)Zn_(3.71)Y_(0.79) alloy was prepared by high pressure solidification.By comparison with the conventional casting alloy,the true stress-strain curve characteristic and deformation microstructure of Mg_(95.50)Zn_(3.71)Y_(0.79) alloy solidified under high pressure were studied via unilateralism compress tests under the strain rate of 0.001–1 s~(–1) and deformation temperature of 523–623 K.Constitutive equations were constructed.According to the experimental results,compared to the conventional casting alloy,the true stress-strain curve of the fine-grain alloy solidified under high pressure not only had the high strain hardening characteristic but the dynamic recrystallization softening after the peak stress was more than the working hardening and would soon reach a stable flow stress- strain state.The deformation activation energy of the alloy solidified under high pressure was 151 kJ/mol,around 49 kJ/mol lower than that of the conventional casting alloy.The fine-grain Mg-Zn-Y alloy solidified under high pressure could obtain 95 percent of dynamic recrystallization grain at 573 K during hot deformation process. (95.50) Zn_ (3.71) Y_ (0.79) alloy was prepared by high pressure solidification.By comparison with the conventional casting alloy, the true stress-strain curve characteristic and deformation microstructure of Mg_ (95.50) Zn_ (3.71) Y 0.79 alloy solidified under high pressure were studied via unilateralism compress tests under the strain rate of 0.001-1 s -1 and deformation temperature of 523-623 K. Constitutive equations were constructed. According to the experimental results, compared with to the conventional casting alloy, the true stress-strain curve of the fine-grain alloy solidified under high pressure not only had the high strain hardening characteristic but the dynamic recrystallization softening after the peak stress was more than the working hardening and would soon reach a stable flow stress-strain state. deformation of energy of the alloy solidified under high pressure was 151 kJ / mol, around 49 kJ / mol lower than that of the conventional casting alloy. fin e-grain Mg-Zn-Y alloy solid under high pressure could obtain 95 percent of dynamic recrystallization grain at 573 K during hot deformation process.