Electroslag metallurgy production practice showed that the initial composition and final slag composition of ANF-6 were very different. The multiple electroslag with different ratio of CaF2 (58%-70%), Al2O3(18%-30%), CaO(0%-12%), SiO2(0%-9.3%) and MgO(0-2.7%) were used to simulate the changes of ANF-6 slag composition in production. Then the melting point, density, viscosity, surface tension and electrical conductivity of different slags were measured respectively. The results demonstrated that, with the content of CaF2 and Al2O3 decreasing, and the content of CaO, SiO2 and MgO increasing, the melting point first increased and then decreased(increased from 1339°C to 1350°C, and then dropped to 1297°C), the density gradually decreased(from 2.96g/cm3 to 2.28 g/cm3), viscosity first decreased and then increased(reduced from 0.097Pa.s to 0.015Pa.s,then gradually rose to 0.083Pa.s), the surface tension increased gradually(from 0.3N/m to 0.39N/m), the conductivity first increased and then decreased(reduced sharply from 3.33S/cm to 3.17S/cm,then increased slowly to 3.30S/cm, decreased gradually to 2.83S/cm). The changes of physical properties of slag would cause changes in operating parameters. In order to get good electroslag ingots, the electrical parameters, process parameters should be adjusted according to the properties changes timely in electroslag refining process.