Abstract: Mould flux is a very important function material in continuous casting process.The viscosity of flux under high frequency electromagnetic field were tested by rotational viscosity tester and a measurement device for electromagnetic characteristics of flux viscosity under high temperature conditions.With finite element finite element,the flow field of flux under high frequency electromagnetic field were simulated.The results show that high frequency electromagnetic field make the flux viscosity rising significantly.With basicity rising(R=0.66~0.91),the viscosity increasing rate at 1 300℃ grows larger,but the melting temperature incressing rate decreasing gradually.It may be the main reason for the significant increasing of flux that the electromagnetic forces disrupt the ordered structure of flux and make the ion rate increaseing.