This study was purposed to investigate the efficacy and feasibility of recombinant humanized anti-CD25 monoclonal antibody for treating steroid-resistant acute graft-versus-host disease (aGVHD ) following allo-hematopoietic stem cell transplantation (allo-HSCT) . Twenty-one cases with II-IV grade steroid-resistant aGVHD after allo-HSCT were treated by intravenous injection of recombinant humanized anti-CD25 monoclonal antibody at a dose of 1 mg/(kg·d) on days 1, 4, 8. Injection was repeated after 1 week for the patients who did not achieve CR. The results indicated that 13 cases (61.9%) got complete response (CR), 4 cases out of them have been still in disease-free survival, 8 cases have been in survival with mild cGVHD, 1 cases died from AML relapse, 6 cases (28.57%) got partial response (PR), 3 cases out of them have been in survival with mild cGVHD, 3 case died from pulmonary infection, 2 cases without response died from GVHD. Overall response rate was 90.5% and long term survival rate was 71.48%. There were no infusion-associated side-effects after treatment with recombinant humanized anti-CD25 monoclonal antibody.It is concluded that recombinant humanized anti-CD25 monoclonal antibody is effective and feasible for treatment of steroid-refractory grade II-IV aGVHD after allo-HSCT.