Rare-earth elements, as modifiers, exhibit high effectiveness in microalloying, inclusion modification, microstructural optimization, and grain refinement. To improve the comprehensive mechanical properties and service performance of heavy rail steel for complex railway operating conditions, U71Mn heavy rail steels with different La-Ce mixed rare-earth contents were melted in a vacuum induction furnace. The evolution of inclusions was characterized and analyzed using FactSage, SEM, and automatic inclusion analysis software. Vickers microhardness, impact resistance at room and low temperatures, and tensile properties were also tested, together with fracture morphology analysis. The results showed that rare-earth addition transformed the inclusion system from MnS- and silicate-dominated inclusions to (La, Ce)₂O₂S-dominated inclusions. Owing to spheroidization modification, the inclusion morphology evolved from irregular shapes to spherical or ellipsoidal forms. The number of inclusions within the scanned field progressively decreased, with the increasing of rare-earth content. As the total mixed rare-earth content increased from 0 to 0.026%, the microhardness increased from 278 to 287 and 294 HV₃, the yield strength increased from 538 to 582 and 610 MPa, the tensile strength increased from 907 to 948 and 978 MPa, and the elongation after fracture increased from 8.00% to 11.73% and 19.13%. The impact energies at room temperature, -20 and -40 ℃ reached maximum values of 7.6, 7.4, and 6.8 J, respectively, with maximum increases of 52.00%, 54.17% and 112.5% compared with the steel without rare-earth addition. The coefficient of variation of microhardness first increased and then decreased, reaching a minimum of approximately 4.80% at a total rare-earth content of 0.026%, indicating improved homogeneity of the microstructure and mechanical properties.