The invention provides a method for improving the grade of the titanium dioxide in the blast furnace slag, which comprises the following steps: the blast furnace slag is pre-treated under the high temperature, so that the titanium in the blast furnace slag forms a structure that is not dissolved in the acid; the blast furnace slag that is pre-treated in the high temperature is dipped in the acid; the blast furnace slag that is dipped in the acid is filtered and washed to get the filtrate; the filtrate after being washed is calcined in the high temperature to get the titanium raw material. The method has low cost, and realizes the effective utilization of the valuable element in the blast furnace slag, and has double benefits of environmental protection and energy conservation.