Abstract: The 65 Mn steel with different contents of cerium were prepared by a vacuum induction furnace. Optical microscope,SEM,EDS and XRD were employed to analyze the influence of rare earth element on microstructure and mechanical properties of 65 Mn steel. The results are shown as follows: when the content of Ce is within 0~0.0046 %, the cleanliness of molten steel is greatly improved. Large strip Mn S inclusions are transformed into spherical composite inclusions containing MnS and Ce₃S₄ complex inclusions with size below 2 μm. The large oxide inclusions of around 11 μm in size with clear edges and irregular shape are transformed into smooth spherical oxide+Ce₂O₂S+Ce₂O₃ complex inclusions with size less than 2 μm. The size of pearlites decreases from 21.65 μm to 13.74 μm,the lamellar spacing of pearlites reduces from 264 nm to 116.77 nm. The mechanical properties of the steel is improved with Ce content. When the content of Ce is 0.004 6%,the yield strength,tensile strength,elongation and impact toughness reach to 714.38 MPa,864.70 MPa,22.75% and 37 J respectively.