Abstract��The ASP continuous caster used in AISC was all equipped with VAI SMART sector section as well as dynamic soft reduction techniques. In order to sufficiently play the role of this certain continuous caster��s effect on enhancing the inner quality of casting billet, experimentally study towards dynamic soft reduction of pipeline steel casting was adopted in this paper. The design principle was studied by analyzing the formulation mechanism of central segregation. With dendrite test and chemical analysis, the effect of element segregation of carbon, manganese and phosphor at different soft reduction position was studied. By all these, the current dynamic soft reduction position was optimized, which would enhance the inner quality of casting billet of pipeline steel.