This study is to investigate the effect of ZL-004 on normal mouse and mice with leukopenia   induced by chemotherapeutic agents.  5-Fluorouracil were administered intraperitoneally to mice to develop leucopenia, and the mice were treated with ZL-004.  The number of peripheral leukocytes and the percentage of granulocyte in total WBC were examined.  The results are that ZL-004 markedly raise peripheral blood leukocytes in the normal mice and the mice model of leukopenia.  So, ZL-004 could protect mice against 5-fluorouracil damage and raise peripheral blood leukocyte.  Features of bone marrow smears is myeloproliferative hyperactivity in the mice, particularly the matured granulocytic series were observed.  The mechanism of ZL-004 is to act on the mouse bone marrow causing proliferation and differentiation.