Abstract: To study the changing of whole blood T-lymphocytes subsets in severe hepatitis patients and its effect on the prognosis.46 patients severe hepatitis of (including 17 dead cases and 29 surviving cases who had been hospitalized from July, 2002 to December, 2004) and 40 chronic hepatitis B patients' T-lymphocytes subsets were detected by flow cytometry.From the changes of T lymphocytes subsets we compared their related clinical prognosis of each case.Results: The average CD3+, CD4+CD8-, CD4-CD8+lymphocytes counts in severe hepatitis group were lower than chronic hepatitis controls groups There could be detected a lot of puerile CD4+CD8+ lymphocytes in severe hepatitis group, whose counts were higher than chronic hepatitis group, The counts of CD3+ lymphocyte in severe hepatitis dead group were lowe than recover group, The count of CD4+CD8+ lymphocytes in death groups were higher than that of recover groups. (P=0.005) .The CD3+, CD4+CD8+, CD4-CD8+ lymphocytes was gradually increasing in severe hepatitis surviving group with the progress of clinical recovering while remained in low level in dead group for long.The CD4+CD8+ lymphocytes was gradually deceasing in severe hepatitis surviving group with the progress of clinical recovering while was increasing in severe hepatitis dead group.Conclusion: The changes of T-lymphocytes subsets especially the elevation of counts of CD4+CD8+ lymphocytes may be one important marker to predict the clinical prognosis.