Irradiation induces severe damage in the hematopoietic system, which leads to bone marrow hyperplasia, pancytopenia, and aggravated tissue formation in bone marrow. Studies have shown that Toll-like receptor 4 (TLR4) has a protective effect against irradiation, but the underlying mechanism remains unclear. In this study, we used a TLR4 knockout (TLR4-/-) mouse irradiation model and found that the white blood cell and platelet counts in the peripheral blood of TLR4-/- mice recovered slowly after irradiation, with bone marrow hyperplasia and increased mortality. Additionally, we found that the proportion of CD11b+Gr1+ granulocytes in the peripheral blood and bone marrow of TLR4-/- mice was lower than that of wild-type mice after irradiation. Further, we found that the expression of NADPH Oxidases (NOXs) in the bone marrow was down-regulated after irradiation of TLR4-/- mice, and administration of the NOXs inhibitor VAS2870 reduced the proportion of CD11b+Gr1+ cells in the bone marrow and peripheral blood of wild-type mice after irradiation. Irradiation induced severe marrow adipocytes accumulation in TLR4-/- mice, TLR4 ligand lipopolysaccharide promoted proliferation and inhibited adipogenic differentiation of mesenchymal stromal cells. In summary, our data suggest that TLR4 promotes myeloid hyperplasia by up-regulating the expression of NOXs after irradiation, prohibits marrow adipogensis and increases the tolerance of mice to irradiation. Copyright © 2019 Elsevier Inc. All rights reserved.