Objective To investigate the effects of ulinastatin on the number of peripheral blood lymphocyte and the percentage of its subsets in patients with severe sepsis. Methods The scores of APECHE II and SOFA, the number of lymphocyte and the percentage of different subsets in these sepsis patients at different treatment time were measured. Results After treatment, the scores of APECHE II and SOFA of severe sepsis patients were decreased, the number of lymphocyte elevated and the percentages of different subset were corrected. Sepsis caused by Gram- positive pathogens had stronger suppression of peripheral blood lymphocyte and subsets compared with Gram - negative pathogens. Conclusion Patients with severe sepsis had less peripheral blood lymphocyte and abnormal subsets. Ulinastatin could help to correct such abnormality.