The invention provides a method for detecting iron content in a water sample by using a methyl-hydroxamic acid spectrophotometric method. The method comprises the following steps of 1) Fe standard solution preparation; 2) absorbance measurement, wherein 1.5-2.5 milliliters of methyl-hydroxamic acid solution with concentration of 0.207 mole per liter, 1 milliliter of 1+1hydrochloric acid, 5.0 milliliters of a buffer solution with a pH value of 1.5-2.5 and 3.0-5.0 milliliters of 3% of H202 are respectively added into a plurality of Fe standard solutions with different volume amounts and then shaken well, constant volume of 25 milliliters is carried out with distilled water, 1 centimeter of cuvette is adopted, the absorbance is measured by taking reagent blank as reference at the position ofa maximum absorption wavelength; 3) standard curve drawing, wherein the iron content serves as the abscissa, the corresponding absorbance serves as the ordinate, the standard curve is drawn, and a regression equation of the standard curve is calculated; and 4) to-be-measured Fe solution measurement, wherein the absorbance of a to-be-measured Fe<3+> solution is measured, and the iron content of theto-be-measured Fe solution is obtained according to the absorbance. The method for detecting the iron content in the water sample by using the methyl-hydroxamic acid spectrophotometric method has theadvantages that the chromogenic reaction and application of the methyl-hydroxamic acid and iron are studied, the method is applied to the measurement of the iron in the water sample, the recovery rate is 95.5-97.8%, the selectivity is good, and the operation is simple and convenient.