In order to understand drug resistance and tetracycline resistance gene of Streptococcus agalactiae epidemic strains,the prevalent strains of S. agalactiae from the main bovine culture area of Inner Mongolia Autonomous Region were detected through Kirby-B auer（K-B） method and PCR.Drug susceptibility testing indicated that the S. agalactiae isolated strains were sensitive to most antibiotics.The S. agalactiae isolates were susceptible topenicillin,cefotaxime,cefazolin,amoxicillin,erythromycin,ciprofloxacin,enrofloxacin,ofloxacin,clindamycin,nitrofurantoin,and vancomycin with susceptibilities rates of 90％ to 100％.In contrast,the S. agalactiae isolates were resistant to tetracycline with resistance rates of 77.27%.Four resistance genes including tetM,tet O,tetK,and tetL were characterized by PCR. All strains carried the resistance gene tetM and 7 strains also carried the resistance gene tetK. The resistance genes tetO and tetL were not detected.The results indicated that the resistance gene were related to the resistant type of antimicrobial agents and was important for further research and clinical therapy resistance mechanisms.