Effects of TiO2 on the viscous characteristic of mold fluxes for the stainless steel were investigated by the rotary viscometer, TEM and XRD. The results showed that with the increasing amount of additive TiO2, the viscosity and solidification temperature of mold fluxes could decrease gradually, and then increase rapidly. The viscosity and solidification temperature of mold fluxes were minimum of 0.30Pa.s (1300°С ) and 1198°С respectively, as amount of additive TiO2 was 10mass%. The viscosity of mold fluxes could be decreased by the additive TiO2 which played the role of network modifier, and could be increased by the precipitation of perovskite (CaTiO3) crystals as amount of additive TiO2 was more than the critical value. The growth of cuspidine and wollastonite crystals could be restrained, and the precipitation of perovskite and melilite crystals could be promoted by the additive TiO2. In this study, the solubility of additive TiO2 was more than 20mass% in mold fluxes at 1350°С .