Abstract: Objective To compare the antibacterial effect of cadazolid and linezolid to Clostridium difficile with different genotype and toxin type, and the effect of cadazolid on the formation of C. difficile spores. Methods The sensitivity of 10 strains of C. difficile, 1 strain of C. lostridium perfringens and 1 strain of Bacteroides fragilis to cadazolid and linezolid were tested. The MICs of cadazolid and linezolid to the tested strains were obtained. One strain of C. difficile(ATCC BAA-1803, RT027) was selected to evaluate the effect of cadazolid on the spore formation of the strain. Results The MIC of cadazolid to C. difficile was 0.25 g/ml (0.03-0.25 g/ml), the MIC of linezolid to C. difficile was 4.0 g/ml (0.5-16.0 g/ml), the MIC of cadazolid was 16 times lower than that of linezolid. The two antibiotics had good antibacterial effect to C. difficile with different genotype and toxin type, and also had antibacterial effect on C. perfringens. Cadazolid had no inhibitory effect on B. fragilis, while linezolid had such effect. Cadazolid could inhibit the formation of C. difficile spores. Conclusion C. difficile is sensitive to cadazolid, indicating thatcadazolid is effective in the clinical treatment of C. difficile infection.