Macrostructure, microstructure and mechanical properties study of commercially pure magnesium satisfied. Macrostructure is characterized by the presence of the columnar structure with crystallites up to 5 mm in diameter and 30 mm long, elongated in the direction of the heat sink. Electron microscopy revealed the presence of dislocation loops and α-dislocations and twins of different orientations prior to the onset of plastic deformation. Found that the mechanical properties of cast magnesium are highly dependent on preferential crystallographic orientation of the sample. Hardening curves cast magnesium have extreme character with a maximum at strains 10-15%.