Objective To study the effects of parecoxib sodium combined with continuous femoral nerve block on the balance of Th1/Th2 in elderly patients after total knee arthroplasty. Methods Fifty elderly patients,33 males and 1 7 females,aged 65 to 80 years,with ASA Ⅰ or Ⅱtreated with total knee arthroplasty were randomly divided into two groups (n =25 each):parecoxib sodium combined with continuous femoral nerve block group (group A)and parecoxib sodium com-bined with intravenous analgesia group (group B).Quick induce laryngeal mask anesthesia and intra-venous parecoxib sodium 40 mg at 30 min before skin incision were adopted in both groups.After the first 8 h,parecoxib sodium of 40 mg was intravenously injected again.The patients in group A re-ceived femoral nerve puncture and continuous electronic analgesia pump.The patients in group B re-ceived postoperative intravenous electronic analgesia pump.Visual analogue score(VAS)during rest and movement at 6,12,24,36,48 h after operation,side effects in two groups were recorded,venous blood samples were taken before anesthesia (T0 ),at the end of operation (T1 ),and 24 h(T2 ),48 h (T3 ),72 h (T4 )after operation for determination of plasma IFN-γ,IL-10 and cortisol (Cor). Results The values of VAS were significantly lower in group A compared with group B in rest at 6, 12 h after operation,the values of VAS were significantly lower in group A compared with group B in moving at every time points after surgery (P <0.05 ).The plasma Cor concentrations were signifi-cantly increased at T1-T3 compared with baseline value at T0 in two groups(P <0.05 ).The plasma Cor concentrations in group A were significantly decreased compared with group B at T1-T3 (P <0.05).The plasma IFN-γconcentrations were significantly lower at T2 and T3 compared with baseline value at T0 in group A,the plasma IFN-γ concentrations were significantly lower at T2-T4 compared with baseline value at T0 in group B (P <0.05),the plasma IFN-γ concentrations were significantly increased in group A compared with group B at T2-T4 (P <0.05 ).The plasma IL-10 concentrations were significantly increased compared with baseline value at T1-T4 in two groups (P < 0.05 ),the plasma IL-10 concentrations were significantly decreased in group A compared with group B at T1-T4 (P <0.05).Compared with group B,the incidence of postoperative nausea,vomiting and pruritus in group A was lowered significantly (P <0.05).Conclusion Parecoxib sodium combined with continu-ous femoral nerve block on postoperative pain in elderly patients after total knee arthroplasty can a-chieve good effect of postoperative analgesia and fewer complications, lower cortisol secretion, slowing down the decrease of IFN-γ secretion and the increase of IL-10 secretion.This method could effectively protect the immune function of patients undergoing arthroplasty.