A numerical simulation study for the multiphase phenomena of magnetic field, liquid steel flow field and inclusion behavior was described, in which the coupled effects of electromagnetic brake (EMBr) and argon gas injection in the slab continuous casting mold with high casting speed were considered. The effects of the EMBr and argon gas flow rate on the liquid steel flow and inclusion removal rate have been investigated. The results show that EMBr could slow down the flow velocity of liquid steel effectively, especially near the meniscus surface, but it had no helpful for the removal of small inclusions and the removal rate for the inclusion particles in diameter range of 5 - 50 mu m reduced from 6.7% without EMBr and argon gas injection to 3.3% with EMBr in the mold. The argon gas injection could increase the liquid steel flow up tendency of the upper circulating area and the floating up rate of inclusion particles with the size 5 - 50 mu m increased to 8.9%. The increase of argon gas flow rate resulted in a stronger eddy zone near the free surface especially near the submerged entry nozzle (SEN) and formed the secondary vortex flow easily, which impacted the fluctuation of free surface and the slag entrapment. The double action of EMBr and argon gas injection could increase the floating up rate of inclusions and the removal rate of small inclusions with the size 5 - 50 mu m increased to 12.2% and the rate for inclusions to be trapped into solidified shell was reduced to 64.4%.