A high performance liquid chromatography with post-column photochemical derivatization method has been developed for the simultaneous determination of aflatoxins B1, B2, G1 and G2 in feed and feed stuffs. The samples were extracted with methanol-water solution (80∶20,V/V), and were cleaned up by immunoaffinity columns. The separation of aflatoxins B1, B2, G1 and G2 were conducted by HPLC, the determination was carried out by fluorescence detector after photochemical derivatization and quantified by external standard method. Under the optimal conditions, the linear range was 0.38 ~ 20.00 µg/L, and that of the correlation coefficients were 0.999 6 ~ 0.999 9, the average recovery rates of aflatoxins B1, B2, G1 and G2 in feed and feed stuffs samples were in the range of 81.9% ~ 98.7% when spiked 0.75 ~ 20.00 µg/kg, inner-day RSD ranged from 1.57% to 3.87%, inter-day RSD ranged from 3.01% to 6.87%, the detection limits (S/N=3) of aflatoxins B1, B2, G1 and G2 were 0.05, 0.02, 0.05 and 0.08 µg/kg, respectively. The method is simple, high in sensitivity and good in repeatability, which had produced satisfactory results in determination of aflatoxins in feed and feed stuffs.