As veterinary medicine industry has grown up steadily, the government quality control of veterinary medicine in market has been performed since 1964. The result of post-market surveillance assay from 2009 to 2012 was analyzed in this study. The average violation rate of all veterinary medicines, was 3.2%, 2.8%, 2.8% and 1.4% in 2009, 2010, 2011 and 2012, respectively. The total average violation rate in the category of antibiotics, other drugs except antibiotics, biologics were 1.2%, 4.4% and 0.8%, respectively. The violations due to insufficiency of major active ingredient content occupied 76.7% among the total violations. The most frequent violated in antibiotics were ampicillin and tylosin, followed by sulfonamides, penicillins etc. In case of other drugs except antibiotics, vitamin A and glucocorticoids (dexamethasone and prednisolone) were violated frequently. The overall trend of violation rates gradually decreased from 2009 to 2012, suggesting that quality of veterinary medicines has improved according to Korea Veterinary Good Manufacturing Practice (KVGMP) system settled down in 1988.