Abstract: [Objective] The purpose of the present study is to investigate the antimicrobial type of florfenicol against the main primary causative bacteria of pig pneumonia.[Method]The minimum inhibitory concentration(MIC),minimal bactericidal concentration(MBC)and post-antibiotic effect(PAE)of florfenicol against Streptococcus suis,Pasteurella multocida and Actinobacillus pleuropneumoniae were determined.[Result]The MIC and MBC of florfenicol against the above pathogenic bacterias were 0.25～0.5 μg/mL and 2～4 μg/mL,respectively.The results have shown that the PAE increased with the increasing of drug concentration and extension of expose time,and time-kill curve also demonstrated that the antibacterial ability increased with the increasing of florfenicol concentration.[Conclusion]According to the results of PAE and time-kill curve in this study,we concluded that the florfenicol is typically concentration dependent against the main primary causative bacteria.