Abstract: <FONT face=Verdana>In the new process of non-blast furnace smelting vanadium-titanium (V-Ti) magnetite developed by Pangang Corp.,the part of V-Ti magnetite rotary hearth furnace direct reduction of iron-slag separation had completed its industrial experiment.Molten iron containing vanadium and deep reduction slag containing titanium dioxide with mass fraction of around 43% were obtained in the experiment.Chemical composition and phase characteristics of deep reduction slag were analyzed.Influences of factors，such as pretreatment,mass ratio of acid to mineral,mass fraction of reactive acid,triggering temperature,and aging temperature,on acid hydrolysis rate of deep reduction slag were systematically investigated.Optimum acid hydrolysis parameters were found,which made a good foundation for the recovery of titanium in deep reduction slag by sulfuric acid method.Results showed that pretreatment made acid hydrolysis rate increased by about 10%.Optimum conditions for acid hydrolysis after pretreatment of deep reduction slag were as follows:mass ratio of acid to mineral was (1.7 ~ 1.8) ∶1,mass fraction of reactive acid was 88%~89%,triggering temperature was 100~120 ℃,and aging temperature was 220 ℃.</FONT>