To evaluate the clinical efficacy of recombinant human Interleukin 11 in the treatment of pre-aplastic anemia, six patients with pre-aplastic anemia were injected with rhIL-11 of 6 million units once a day during 7-14 days. Blood platelet counts were taken on day 8, 15, 30 and 60 after the treatment, and bone marrow examination was performed on day 15 as compared with those before treatment. The results showed that platelet counts in 3 out of 6 patients increased remarkably (50%), one of the six increased moderately (16.7%), another case of the six increased slightly (16.7%), platelet in one out of six did not significantly increase (16.7%), the total efficacy rate is 83.3%, the amount of megakaryocyte in bone marrow of all six patients increased, the side effect of the rhIL-11 treatment was light. In conclusion, the efficacy of recombinant human Interleukin-11 in the treatment of thrombocytopenia patients with pre-aplastic anemia is satisfactory. As the number of the cases is too small to conclude, further exploration needs accumulation of more applications.