The invention discloses a method for preparing ilmenite by ilmenite carbothermic-electrolysis, and belongs to the field of electrochemical metallurgy. The method for preparing ilmenite by the ilmenitecarbothermic-electrolysis comprises the steps that ilmenite and reducing agent carbon are evenly mixed in proportion, and then the mixture is placed into molten oxide electrolyte; carbothermic reduction is carried out on the ilmenite in the electrolyte to obtain molten iron; graphite or inert electrode is used as anode, a graphite rod or an inert metal rod is inserted into the molten iron as cathode, and a constant potential or constant current method is adopted for electrolysis; electrochemical deposition is carried out on the cathode molten iron after electrolysis to obtain ferrotitanium alloy products; after the content of iron and titanium in the electrolyte is reduced to a certain value, a mixture of the ilmenite and the reducing agent carbon is added to the electrolyte again for thenext cycle; and when the titanium content in the molten iron increases to a certain amount or reaches the required ferrotitanium alloy ratio, the liquid ferrotitanium alloy products are discharged through a tapping hole in the bottom of a crucible, and the next cycle is continued. The method for preparing the ilmenite by the ilmenite carbothermic-electrolysis has the characteristics of short flow, simple operation, low equipment requirement, high titanium element recovery rate in the ilmenite, no waste residue and waste water, green and cleanness.