Abstract: A method was established for the determination of the content of parathion and isofenphos-methyl in plant food by gas chromatography. The method was validated by FPD detector, external standard method and automatic injection, the results showed that the detection limits of parathion and isofenphos-methyl were 2 μg/kg （1 μL, S/N=3）, the recoveries of parathion and isofenphos-methyl were 86.7%~94.5%, 89.3%~92.6%, the RSD（n=10） of parathion and isofenphos-methyl were 3.86% and 4.23% respectively.

Key words: external standard method, plant food, parathion, isofenphos-methyl