The invention discloses a method for determining aflatoxin. The method is characterized by comprising the following steps: (1) preparing a solution 1 for later use; (2) preparing a solution 2 for later use; (3) preparing R1 modified by HRP (horseradish peroxidase); (4) preparing R2 modified by HRP; and (5) detecting aflatoxin. Red rhodamine B can neither cause concentration quenching, nor cause insufficient light intensity. By adding mica powder, the luminescence lifetime of an oxalate luminescence system is significantly prolonged. Ruthenium terpyridine and chemiluminescence have the advantages of high detection sensitivity, wide linear range and the like, and aflatoxin can be detected more effectively. The method disclosed by the invention has the excellent properties of lower toxicity, higher flash point and lower vapor pressure. By detecting the content of aflatoxin in liquid milk and using a standard addition recovery method, the recovery yield of 98.4%-100.4% is obtained, indicating that the method has good accuracy in determination of aflatoxin.