Abstract: The mechanism of action of nucleating agent was studied during the direct reduction of low grade hematite pellets in Central South China.The results show that the nucleating barrier is reduced by over 50% by adding a nucleating agent in the hematite pellets,which can effectively improve the nucleating of metal iron grains during the direct reduction.Because of the nucleating agent,the apparent activation energy of the hematite pellets decreases from 18.10 kJ·mol^-1 to 10.15 kJ·mol^-1,dropping by 43.92%.The lower the apparent activation energy,the easier the reduction reaction takes place.It is concluded that the nucleating agent can efficiently improve the direct reduction and upgrade the metallization degree of the reduced pellets.