Abstract: The objective of the present study is to provide guidance on the rational use of veterinary drugs in livestock and poultry farms and avoid the impacts of overdosed veterinary drugs on the quality and economic benefits of animal products. In this article, based on the use data of veterinary drugs by layer farmers obtained in field survey, the author analyzed the key factors affecting layer farmers’excessive use of veterinary drugs with the quantile regression method. The results showed that there was excessive use of veterinary drugs, and it was a bounded rational behavior of the farmers under the principle of utility maximization. Through empirical analysis, it was found that scale development had effectively guided layer farmers to use veterinary drugs in a scientific and rational way; layer breeding training and improvement of veterinary drugs quality had effectively restrained the excessive use of veterinary drugs by farmers; risk- avoiding farmers would not use excessive veterinary drugs as they took the risks of excessive use of veterinary drugs into consideration. According to the results, the author put forward some countermeasures, such as pushing on large-scale and standard livestock breeding, strengthening the training of veterinary drug use in livestock and poultry farms, and enhancing the quality of veterinary drugs, thus to promote and guide the reasonable use of veterinary drugs in livestock and poultry farms in China.