The United State officially imposed anti-dumping measures on Vietnamese catfish from 2003 and such measures still remain in effect. This paper firstly analyses key factors of the dispute and the arguments of both parties on issues which regarding the determination of normal value and calculation of dumping margin for certain frozen fish fillets from Vietnam. The outcome of this paper is to point out the U.S anti-dumping duty on certain frozen fish fillets from Vietnam are inconsistent with the AD Agreement