The invention relates to a method for determining the content of Al, Ca and Fe in highly pure nanometer ITO powder. The method comprises the following steps: carrying out microwave digestion treatment on an ITO sample, and carrying out dry filtration to obtain a solution to be detected; preparing a series of standard solutions of Al, Ca and Fe, wherein the Al, Ca and Fe concentrations of the standard solutions are 0, 20ng/mL, 40ng/mL, 60ng/mL, 80ng/mL and 100ng/mL respectively; selecting working conditions of an inductively coupled plasma mass spectrometer, and selecting <27>Al, <40>Ca and <56>Fe to determine; determining to obtain the work curves of Al, Ca and Fe; and determining to obtain a signal intensity ratio Y<Al>, Y<Ca> and Y<Fe> of <27>Al, <40>Ca and <56>Fe in a blank solution and the ITO solution to be detected to an internal standard Sc element, and calculating to obtain the mass percentages of Al, Ca and Fe in the ITO sample. The method allows the detection result to be highly reliable, and can well meet the analysis of the ITO material with the content of Al, Ca and Fe of 0.0001-0.010%.