Abstract: In this study, Sheldrake was used as the animal model, and we tested the proliferation of its T lymphocyte after infected by duck Tembusu virus.The result showed that after duck Tembusu virus infection, stimulation index of peripheral blood lymphocyte of test group increased first and then decreased, and recovered again.Lymphocyte stimulation index of test group was significantly (P<0.01) higher than that of control group at3dpi (day post-infected) , and then decreased to the level of control group at 5dpi, and was significantly lower (P<0.05) than that of control group at 7dpi and 15 dpi, and then recovered to the level of control group at 21 dpi.The result indicated that duck Tembusu virus infection could cause the duck T lymphocyte immune suppression during 7dpi to 21 dpi.