Abstract:FH40 experimental steel with different Ce content was prepared by vacuum induction furnace. The rolling microstructure of the steel was observed by OM, SEM, TEM and EDS, and its tensile properties and fracture morphology were tested and analyzed. The influence mechanism of Ce on the rolling microstructure and tensile properties of FH40 steel was studied.The results show that with the increase of Ce content from 0 to 0.058%, the rolling microstructure of the steel was refined. The rolling microstructure changed from polygonal ferrite to fine equiaxed ferrite, with the formation of granular bainite. The composite inclusion sof Ce-O-S+TiN and Ce-O-S were produced in the steel containing 0.0273%Ce and 0.058%Ce, with four and five pieces of IAF induced, respectively.The yield strength and tensile strength of the experimental steel containing 0.058%Ce are 31MPa and 33MPa higher than that of the experimental steel without Ce respectively.The experimental steels showed dislocation strengthening and second phase strengthening. The precipitates in the experimental steel without Ce was mainly the composite phase of Nb-Ti. Nb-Ti-Ce was the main composite phase in the experimental steel containing 0.058%Ce, and being more dispersive and fine with higher dislocation density. The fracture morphology is more uniform. The dimple became larger and deeper, which makes it more difficult to fracture under the action of shear stress, thus improving the tensile strength of steel.