The invention belongs to the technical field of analytical chemistry, and relates to a method for detecting nitrite ions based on ratio type colorimetry. The method comprises the following steps: sequentially adding 25 [mu] L of 1 mg / mL hollow MnFeO suspension, 30 [mu] L of 5 mM TMB solution and 1440 [mu] L of 0.2 M acetate buffer solution into a 2 mL centrifugal tube, and uniformly mixing; respectively adding NO2 <-> with different concentrations, wherein the final concentrations of the NO2 <-> in the system are respectively 3.33 [mu] M, 6.67 [mu] M, 10 [mu] M, 13.33 [mu] M, 20 [mu] M, 33.33 [mu] M, 50 [mu] M, 66.67 [mu] M, 83.33 [mu] M, 100 [mu] M, 120 [mu] M and 133.33 [mu] M; measuring an absorption spectrum by using an ultraviolet-visible absorption spectrophotometer, and drawing a standard working curve; and measuring an absorption spectrum of a to-be-measured NO2<->sample, and comparing the absorption spectrum with the standard working curve to obtain the NO2<-> concentration of the sample. According to the invention, the oxidation product TMBox of the hollow MnFeO + TMB system and the nitrite are subjected to a diazotization reaction so as to achieve the indirect detection of the nitrite, the detection process conditions are mild, the detection limit is as low as 0.2 [mu] M, and the detection of the nitrite in the food can be achieved.