Abstract: The research subject of this study was sixteen strains of lactobacillus which separated from milk of Damao pastoral areas of Inner Mongolia,and paper diffusion method was used to test the drug resistance of four kinds of antibacterial drugs of ofloxacin,ciprofloxacin,norfloxacin,and streptomycin. The results showed that 93.75% of sixteen strains of lactobacillus were resistant to ofloxacin and streptomycin,and 100% of sixteen strains of lactobacillus were resistant to ciprofloxacin and norfloxacin.The results of PCR amplification and amino acid sequence analysis for all drug resistance lactobacillus showed that the resistance of one strains of lactobacillus was related to mutation of gyr A gene.