The invention discloses a method for determination of aflatoxin. The invention is innovative by comprising the following steps: 1) weighing a sample, adding an acetonitrile-water extract, stirring for 30 minutes, and then filtering by using qualitative paper, wherein the acetonitrile and water are in the volume ratio of 84:16; 2) determining the sample under the following conditions: chromatographic conditions of a liquid chromatographic column AgilentSBC-18 (25 cm*4.6 mm), a mobile phase of 85 v% of acetonitrile and 15 v% of water, column temperature at 30 DEG C, sample size of 25 mL and flow rate of 1.0 mL / min; 8 mL of extraction filtering liquid to a multifunctional purification column, transferring 2 mL of purification liquid from a collection pool of a purification column into a derivative bottle, blowing nitrogen at 60 DEG C, adding 200 mL of normal hexane and 100 mL of trichloroacetic acid, mixing uniformly for 30 s, derivatizing for 15 min at a 40 DEG C baking oven, drying at room temperature, dissolving with 200 uL of water-acetonitrile solution, mixing uniformly, and sending into an automatic sample introduction bottle, and determining. The detection method provided by the invention is simple and fast in operation and accurate and reliable in results, has little pollution, high security, reduced pollution to operation personnel and the environment, and low detection cost, and is easy for popularization.