A phenomenological crystal plasticity constitutive model for magnesium single crystal was presented.Four deformation mechanisms(including basal〈a〉,prismatic〈a〉,pyramidal〈c+a〉 slip and tension twin)and their interactions were considered.Twin-induced lattice reorientation was also incorporated in the model.The proposed model was then applied to the simulation of plane-strain compression deformation for different orientations.Related material parameters were calibrated at first according to the classical channel-die tests.The predicted macro-and microscopic responses,along with the experimental results,show strong orientation-dependent properties.It is also found in the simulation that basal slip in the twinned region is active even before the saturation of twin activity in a twin-favored case.Furthermore,the effect of an initial deviation angle on the mechanical responses was evaluated,which is proved to be also orientation-dependent.Basal slip is found to be easily activated due to a slight deviation,while a slight deviation in the twin-favored case could result in a significant difference in the mechanical behavior after the reorientation.The effort on the study of magnesium single crystal in the present work contributes to further polycrystalline analysis. A phenomenological crystal plasticity constitutive model for magnesium single crystal was presented. Fluid deformation mechanisms (including basal , prismatic , pyramidal slip and tension twin) and their interactions were considered. TWIN-induced lattice reorientation was also incorporated in the model.The proposed model was then applied to the simulation of plane-strain compression deformation for different orientations. Related Material Parameters were calibrated at first according to the classical channel-die tests. predicted macro- and microscopic responses, along with the experimental results, show strong orientation-dependent properties. It is also found in the simulation that basal slip in the twinned region is active even before the saturation of twin activity in a twin-favored case. Futuremore, the effect of an initial deviation angle on the mechanical responses was evaluated, which is proved to be also orientation-dependent.Basal slip is found to be easily activated due to a slight deviation, while a slight deviation in the twin-favored case could result in a significant difference in the mechanical behavior after the reorientation. Effort on the study of magnesium single crystal in the present work contributes to further polycrystalline analysis.