The dynamic soft reduction technology for 360 mm×450 mm bloom casting and its application results at Panzhihua Iron and Steel Co (PISCO) were presented. In order to analyze the influence of the soft reduction on internal defects of bloom, such as center porosity and central segregation, experiment for contrasting process with or without soft reduction for bloom was conducted. The operation shows that after applying the soft reduction of alloy steel 45CrMnMo bloom, the ratio of center porosity whose defect level is less than or equal to 1.0 increased from 66.67% to 85.71%, ratio of central segregation whose defect level is below 1.0 increased from 94.44% to 100%, ratio of central shrinkage cavity which is free increased from 88.89% to 96.42%, and central segregation index of carbon decreased from mean value of 1.15 to 1.05. The dynamic soft reduction technology for 360 mm × 450 mm bloom casting and its application results at Panzhihua Iron and Steel Co (PISCO) were presented. In order to analyze the influence of the soft reduction on internal defects of bloom, such as center porosity and central segregation, experiment for contrasting process with or without soft reduction for bloom was conducted. The operation shows that after applying the soft reduction of alloy steel 45CrMnMo bloom, the ratio of center porosity whose deficient level is less than or equal to 1.0 increased from 66.67 % to 85.71%, ratio of central segregation whose deficient level is 1.0 increased from 94.44% to 100%, ratio of central shrinkage cavity which is free increased from 88.89% to 96.42%, and central segregation index of carbon decreased from mean value of 1.15 to 1.05.