In this paper the mathematical model is established on the behaviour ofreduction and impoverishment of TiO2 in molten slag in smelting silico-titanium ferroalloy usingtitanium bearing slag by electrosilicotherinic procese under experimental conditions.It is studied thatthe influences of smelting conditions,such as smelting temperature,initial basicity of burden,quantity of reductant,smelting time and TiO2 content of slag on the reduction and impoverishmentof TiO2 in molten slag.