Abstract: Numerical simulation of comprehensive metallurgical behavior of liquid steel in slab mold is described.It was found that the flow of liquid steel was decided by the shape and intensity of the jet of SEN.Under the condition of working tip structure of SEN used,the low pressure back flow zone near the side port of SEN result in the liquid steel outflow from the bottom of the sides port and the effective area of sides port became lower.The big fracture surface made the temperature of meniscus get low.The temperature of shell got low with the fracture surface increase.When the size of fracture surface is 1 400 mm×230 mm and 1 600 mm×230 mm,the thickness of narrow side solidification shell of mold outlet is 11.5 mm;the size of fracture surface is 1 800 mm×230 mm,the thickness of narrow side solidification shell of mold outlet is 13.4 mm.The fracture surface has little effect on the thickness of shell of wide sides.