Objective To study the influence of IL-33 on the Hematopoietic stem cells and progenitor cells. Methods Cells from the peripheral blood, spleen, thymus and bone marrow were stained with indicated antibodies and analyzed by flow cytometry. The LT-HSCs were sorted and culture using in vitro clonogenic assay. Results The percentage of B cells and T cells was decreased and the percentage of M cells was increased in the peripheral blood from IL-33 transgenic mice. Compared with the wildtype mice, the number of HSCs, MPPs and CLP was decreased; meanwhile the number of CMP and GMP was increased in the bone marrow from IL-33 transgenic mice. An in vitro clonogenic assay showed that LT-HSCs increased the ability to self-renew from IL-33 transgenic mice. And the percentage of S-G2-M stage hematopoietic stem cell was increased from IL-33 transgenic mice. Conclusion IL-33 increase the myeloid differentiation in hematopoietic stem cells.