A new 3D mathematical model describing the electromagnetic stirring (EMS) in the round billet continuous casting mold was developed and the method combining the finite element--finite volume was used to solve the Maxwell's equations and the turbulent Navier-Stokes equations. The characteristics of magnetic field, flow field, temperature field and inclusion trajectory during EMS were analyzed considering the influences of the exciting current intensity and frequency. The simulated magnetic field in the mold is in good agreement with the measured data in the real steel plant, the electromagnetic force is circumferential distribution at the horizontal section of billet. Molten steel forms two pair of recirculation zones in the longitudinal section of the mold and recirculates at the horizontal section. Most of superheated molten steel is stranded in the upper region of mold, the core temperature of billet reduces dramatically and the temperature gradient at the solidifying forefront of billet increases. Most inclusion particles accumulate in the upper zone of mold and do a swirl--like motion. The flow behaviour, temperature distribution and inclusion motion in the mold are all influenced obviously by the exciting current intensity and frequency.