Veterinary drug plays an irreplaceable role in pig farming. However，improper use will cause the residues of veterinary drugs，as well as causation and spread of drug-resistant bacteria in the food chain system，posing a potential risk to human health. With samples surveyed on 654 pig farmers in Funing of Jiangsu Province，we adopt MVP（Multivariate Probit Model）model to study their behaviors and influencing factors on using veterinary drugs based on earnings expectations method. The survey and research results show that the behavior of excessive use of veterinary drugs and non-compliance with the withdrawal period is common in pig farming，and the proportion of non-compliance with withdrawal period accounting for about 70% of the samples. Farmers’ gender，age，family size，the proportion of farming income in total net income，farming scale，breeding period，cognition of veterinary drug residues and understanding of the government penalties for non-compliance etc. affect their behaviors of veterinary use in varying degrees. Government regulation has a significant effect on the behavior of using human drug in pig farming，while not on the behavior of the excessive use of veterinary drugs and non-compliance with the withdrawal period.