Abstract: Taking medium-carbon 45 steel as the research object, the Pulse Magneto-Oscillation (PMO) homogenization technology was adopted to perform pulse magnetic field treatment on 225×270 rectangular casting billets under high, medium and low power process parameters. The results show that a certain power level is required for PMO treatment. Under high power conditions, the central shrinkage cavity of the casting billet is completely eliminated, the proportion of equiaxed crystals increases by 66.07% and 19.62% respectively, and the central segregation index of the casting billet can be reduced to 1.02. Appropriately reducing the PMO power can still significantly improve the central shrinkage cavity defect and central segregation of the casting billet; however, selecting low PMO power fails to achieve the ideal metallurgical effect. Under the appropriate PMO process parameters, increasing the continuous casting speed has little impact on the PMO homogenization effect.