To investigate the immune functions of CD4+ and CD8+ lymphocyte subsets in peripheral blood of captive-breeding forest musk deer (Moschus berezovskii) and to explore the method for detecting lymphocyte subsets by flow cytometry will provide a scientific basis for studying the pathological mechanism and diagnostic methods of major diseases in this species. Five healthy musk deer and five musk deer with respiratory diseases were selected to compare CD4+ and CD8+ lymphocyte subgroups their peripheral blood by double-color flow cytometry. Data were processed and analyzed by SPSS18.0 software, and statistically described utilizing mean and standard deviation (Mean ± SD). Differences between groups were analyzed by T-test, and P-value < 0.05 was considered significant. The test results showed that flow-cytometric fluorescent antibodies against sheep-derived CD4 and CD8 could label the cells of forest musk deer effectively (Table 1 and Fig. 1, 2). Compared with healthy forest musk deer, the content of CD4+ cells in peripheral blood of diseased forest musk deer increased slightly, but there was no statistical difference (P > 0.05) (Fig. 3), while the content of CD8+ cells decreased significantly (P < 0.01) (Fig. 3), and the ratio of CD4+/CD8+ increased significantly (P < 0.01) (Fig. 3). The changes of CD8+ lymphocyte subsets in peripheral blood of forest musk deer with respiratory inflammatory diseases were significant. Detection of lymphocyte subsets is of great importance in the diagnosis of forest musk deer diseases.