Abstract: In order to improve the inner quality of slabs, a set of dynamic soft reduction models were developed, which include heat transfer, secondary cooling and roll gap control models, and the key parameters of soft reduction were optimized. The models were validated by shooting-pin tests and measuring the surface temperature of slabs. The measurement results agree with those calculated with the models, and the surface temperature fluctuation of slabs can be controlled in a narrower range when the casting speed changes. Production testing at different parameters of soft reduction was applied to optimize the percent reduction and reduction position by macrostructural examination and analyzing the center segregation. The best soft reduction parameters of this casting machine are that the solid ratio is 0.2 to 0.5 and the percent reduction is 1.2 mm· m^-1.