Objective To observe the effect of clindamycin for preventive infection in arthroplasty prophylac-tic.Methods 108 knee replacement patients were injected by 600mg intravenous clindamycin preoperation and con-tinue to use 1 -2 days after operation.The average postoperative hospitalization,postoperative outcome,body tempera-ture and blood after WBC changes of CRP and ESR in the fall of superficial infection trend,the average postoperative day,take out stitches after operation and the number of cases,postoperative deep infection early after infection (2 weeks)and delayed infection cases (within one year)were observed in order to evaluate the efficacy of preopera-tive antibiotics.Results 2 cases had superficial infection due to wound dehiscence (two times after suture recover-y),there was no complications of surgical wound in the other cases.In all cases,after operation,body temperature and blood WBC became to the normal level in seventh days,postoperative patients'CRP,ESR monitoring were significantly higher than those before operation (CRP:F =105.32,P =0.045;ESR:F =118.47,P =0.039),but on the 5 day after operation they were started to decline,CRP in the 21 postoperative day gradually returned to normal,and ESR gradually returned to normal after 6 months of operation.Preoperative HSS score was significantly lower than the post-operative score[(46.8 ±9.7)points vs.(91.7 ±3.4)points,t =6.38,P <0.05].Conclusion Clindamycin plays a definite role in prevention of infection,especially in the beta lactam antibiotic allergy cases,it can be preoperative antibiotic prophylaxis instead of cephalosporins.