<p>The influence of basicity on the melting property, viscosity, activation energy for viscous flow, and structure of Cr-containing molten titanium slag was investigated in this study. The hemisphere and rotating cylinder methods were employed to measure the characteristic temperature and viscosity. The structure of slag was determined by Raman spectroscopy. The results show that with the increase of basicity, the softening temperature, hemispherical temperature, and fluidity temperature of Cr-containing molten titanium slag increased. Within the basicity range of 0.5 to 0.8, the increase in softening temperature and fluidity temperature was not significant. Both of the viscosity and activation energy for viscous flow decreased with the increase of basicity. As the basicity increased from 0.5 to 0.8, the activation energy for viscous flow decreased from 227.77 kJ&#xa0;mol⁻¹ to 213.20 kJ&#xa0;mol⁻¹. With the increase of basicity, the free oxygen in the slag increased. The bridging oxygen in the silicate and titanate network was destroyed by the free oxygen ion, depolymerizing the complex structural unit into simpler structural unit, resulting in the decrease in degree of polymerization of the slag. The results of this study provide a theoretical and technical basis for the comprehensive utilization of Cr-containing molten titanium slag and the sustainable development of titanium resources.</p> Graphical abstract <p></p>