In recent years, ultrafine grained steels have developed by the new thermo-mechanical control processing (TMCP) and the severe plastic deformation (SPD) processes. The minimum ferrite grain size obtained by the new TMCP is less than 1μm. On the other hand, in the SPD processes such as the equal channel angular Extrusion (ECAE), the high pressure torsion process (HPT) and the accumulative roll bonding (ARB), steels with a sub-micron scaled grain size are developed. In order to obtain high-strengthened steel with ductility, carbon steels with various carbon contents were deformed by repetitive side extrusion process and heat treatment, and the properties of materials such as Vickers hardness, tensile strength and microstructure observation were investigated. Vickers hardness and tensile strength increased with increasing number of process. The microstructures of all steels were refined by deformed structure. After heat treatment, the tensile strength became lower and total elongation increased with decreasing hardness. Fatigue property was better than that of the as-received material after side extrusion and heat treatment.