A method for measuring the purity of nickel carbonyl in nickel carbonyl containing carbonyl iron comprises the following steps: performing an oxidizing reaction between a crude nickel carbonyl liquidwith a certain volume V and excessive saturated bromine water; adding excessive citric acid which forms a yellow complex with Fe<3+> to eliminate interference of iron ion; adding a sodium hydroxide solution to adjust the pH value to 8-10; adding an excessive dimethylglyoxime solution to produce a dark red nickel dimethylglyoxime complex; diluting the solution to a certain volume V2; measuring theabsorbancy of the nickel dimethylglyoxime complex solution by use of an ultraviolet spectrophotometer; obtaining the concentration C1 of Ni<4+> in the nickel dimethylglyoxime complex solution according to a drawn standard curve of Ni<4+> standard solutions with different molar concentrations; calculating the amount of a substance of nickel according to the volume V2 of the nickel dimethylglyoximecomplex solution; and then calculating the purity of nickel carbonyl.