The evaluation of microstructure and the thermal diffusivity of copper subjected to severe plastic deformation using multi-axial compression was investigated. The investigations were performed on copper (M1E grade) processed to effective strain at range f =1-14.9. The multi- axial compression resulted in an refining structure. The evolution of dislocation structure, misorientation distribution, crystalline size were observed by using transmission electron microscopy (TEM) and scanning electron microscopy (SEM) equipment with electron back scattered diffraction (EBSD) facility. The thermal diffusivity measurements were performed by using the LFA427 apparatus based on the laser-flash method. Subgrain and grain size for f =3.7 reaches about 250 nm and 550 nm respectively. The local recrystallization occur in analyzed microarea especially at f =7.5 and delay the reduction of sub(grain) size. In consequence no more large changes in structure occur during further processing up to the largest strain. The microstructural phenomena have an influence on the thermal parameters. The value of this parameters insignificantly decreased with increasing of accumulated strain.