Abstract: The physical simulation test method for researching on the role of inclusions in formation nucleation of acicular ferrite was designed and the roles of CuS,Al₂O₃ and Al₂O₃·CuS in nucleation of acicular ferrite were studied.The metallurgical microstructures of the micro zone adjacent to the inclusions were observed with digital metallurgical microscope and the chemical compositions of the micro zone adjacent to the inclusions were analysed with electron probe mircoanalyzer.The results show that CuS and Al₂O₃·CuS can make depleted Mn zones be formed in the metal micro zone adjacent to the inclusions formed,CuS and Al₂O₃·CuS have an ability to induce the nucleation of acicular ferrite;Al₂O₃ can not make the chemical composition of the metal micro zone adjacent to the inclusions change and depleted Mn zones can not be formed,and Al₂O₃ is not potent in nucleating acicular ferrite during thermal cycle.The CuS on inclusion surface plays an important role on the nucleation and growth of acicular ferrite.