Ti5Si3 alloy powders were extracted from Ti-bearing blast furnace slag by solid oxygen ionic membrane controlled oxygen flow metallurgy technology. XRD, SEM and EDX analyses show that calcium, magnesium and aluminum impurities are effectively removed during electrolysis. The products Ti5Si3 from Ti-bearing blast furnace slag have similar microstructure and components with the products from the electrolysis of the mixture of TiO2-SiO2 powder (TiO2:SiO2=5:3). The removal mechanism of impurities was analyzed.