The invention discloses a method for measuring organic nitrogen mineralization rate of a cake fertilizer in soil. The method comprises the following steps of: setting a sample group and a contrast group by using syringe-like vessels, wherein the cake fertilizer with known organic nitrogen amount is mixed in the soil of the sample group, and the cake fertilizer is not added in the contrast group; after the sample group and the contrast group are set, drip washing each sample and each contrast till the existing mineral nitrogen in the sample group and the contrast group is cleaned off; performing aerobic culture on the sample group and the contrast group, drip washing once every 4 to 7 days, receiving the filtrates of each sample and each contrast in containers, measuring the mineral nitrogen content of each filtrate by using a continuous flow analyzer, and covering the upper orifices of the syringe-like vessels by using membranes with pores in the center after drip washing till the culture period is completed, thus obtaining the average mineralization amount difference of organic nitrogen in the samples and the contrasts; and dividing the difference by the organic nitrogen content of the cake fertilizer part in the sample to obtain the organic nitrogen mineralization rate of the cake fertilizer in the soil.