The invention provides a thiocyanate spectrophotometry method for detecting iron content of a high-temperature alloy. The thiocyanate spectrophotometry method comprises the following steps of 1, dissolving a sample by an acid to obtain a sample solution, 2, taking two equal sample solution parts, and adjusting the sample solution parts to color development acidity, 3, adding an ammonium persulfate solution into one of the two equal sample solution parts, carrying out mixing, adding an ammonium thiocyanate solution into the mixture, and diluting the mixed solution to a volume indicated by a scale line so that a color development solution is obtained, 4, diluting the other one of the sample solution parts by water to a volume indicated by a scale line so that a reference solution is obtained, 5, through the reference solution as a reference substance, measuring absorbancy of the color development solution by a spectrophotometer and calculating iron content wFe by a standard curve drawn according to an iron standard solution, and 6, calculating iron content wFe' of a high-temperature alloy according to a formula of w'Fe=wFe+0.0084wCu+0.00244wCo+0.0011wV, wherein wCu, wCo and wV respectively represent mass percentages of Cu, Co and V in the high-temperature alloy. The thiocyanate spectrophotometry method for detecting iron content of a high-temperature alloy has simple processes, high sensitivity, good selectivity and good reappearance, has a wide detection scope and is not interfered by nickel, cobalt, copper and vanadium.