Complex deoxidizer is an important supplementary material for steelmaking,which can not only absorb liquid steel inclusions and improve the quality of molten steel,but also enhance deoxidation,desulfurization, dephosphorization,to prevent the molten steel suction and reduce the molten steel temperature loss.Currently,the complex deoxidizer all contain a certain amount of metal aluminium.The metal aluminium can not be determined for the steel.The entire aluminium contents were regarded as the content of approximate metal aluminium,that often bring great economic losses.Because A1,0,price is cheaper than metal aluminite powder,suppliers added a certain amount of Al_2O_3 in complex deoxidizer,pretend to be the metal aluminium to reap huge profits.This paper put forward a kind of method for determining aluminum,which would reduce loss of the enterprise.Research and put forward an iron triehloride,which extracted from Al metal from complex deoxidizer.Meantime,using orthogonal design of the experiment has been optimized for working conditions.The RSD of the samples are I. 07%-1.94%,the recoveries of the experiment results are 97.0%-110.0%,which expressed the precision and accuracy of the experiment are good.The establishment of the iron triehloride as a extractor,which is rapid and accurate for determination of Al metal in complex deoxidizer. Complex deoxidizer is an important supplementary material for steelmaking, which can not only absorb liquid steel inclusions and improve the quality of molten steel, but also enhance deoxidation, desulfurization, dephosphorization, to prevent the molten steel suction and reduce the molten steel temperature loss. Current , the complex deoxidizer all contain a certain amount of metal aluminum. The entire aluminum contents were considered as the content of approximate metal aluminum, that often bring great economic losses. Since A1, price is cheaper than metal aluminite powder, suppliers added a certain amount of Al_2O_3 in complex deoxidizer, pretend to be the metal aluminum to reap huge profits.This paper put forward a kind of method for determining aluminum, which would reduce loss of the enterprise. Research and put forward an iron triehloride, which extracted from Al metal from complex deoxidizer. Meantime, using orthogonal design of the experiment has been optimized for working conditions. The RSD of the samples are I. 07% -1.94%, the recoveries of the experiment results are 97.0% -110.0%, which expressed the precision and accuracy of the experiment are good. The establishment of the iron triehloride as a extractor, which is rapid and accurate for determination of Al metal in complex deoxidizer.