Abstract: The effects of different rare earth Ce contents on the modification of inclusions and mechanical properties of 316L stainless steel were studied by means of field emission scanning electron microscopy, metallographic microscopy, impact and tensile tests. The results show that the addition of rare earth Ce, the grain size is refined, and the type, shape and size of inclusions are changed. The inclusions in the experimental steel change from the initial MnS and Si-O-Al-Mn inclusions to the Ce-containing Si-O-Al-Mn-Ce+Ce-O and Al-O-Ce-Si-MnS composite rare earth inclusions. The morphology changes from the original long strip and rod to oval and spherical, and the size decreases. With the further increase of Ce content, the inclusions are transformed into Al-O-Ce-Si and Ce-O-S rare earth inclusions, and the morphology is changed from the original long strip, rod shape to spherical shape, and the size is obviously reduced. After adding 0.0082%Ce, the experimental steel has the best mechanical properties. The tensile strength increases from 698.4 MPa to 764.2 MPa, an increase of 9.42%. The yield strength increases from 359.8 MPa to 401.2 MPa, which increases by 11.51%. The impact energy increases from 264.6 J to 289.4 J, an increase of 9.37%. The tensile fracture and impact fracture morphology of the experimental steel are improved, and the number of the dimples at the fracture increases significantly and the distribution is more uniform.