Abstract: The morphology, chemical composition, size and type of inclusions were investigated by experiment and thermodynamic calculation in a micro-alloyed steel deoxidized by Ti, and the structure of this steel was analyzed. The results show that grains are fine after adding Ti in the steel, the deoxidation product of Ti become the nucleus of TiN, or Al₂O₃ becomes the nucleus of the deoxielation product of Ti in solidification of liquid steel. After adding Ti, inclusions are finely distributed in the steel, and grains are fine by using the dispersion of fine inclusions as intragranular ferrite nucleated sites.