Objective To investigate the therapeutic effect of bone marrow cell adoptive therapy on metabolic-dysfunction-associated fatty liver disease (MAFLD) in mice and its possible cell population. Methods The staining was used to detect the liver lesions of MAFLD in C57BL/6 mice induced by methionine and choline deficiency diet (MCD) and the adoptive therapeutic effect of bone marrow cells on MAFLD was evaluated by detecting the levels of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST). The mRNA expressions of low density lipoprotein receptor (LDLR) and interleukin-4 (IL-4) in liver immune cells (including T, NKT, Kupffer cells and other cell populations) were detected by real-time quantitative PCR. The bone marrow cells labeled with 5, 6- carboxyfluorescein diacetate succinimidyl ester (CFSE) were injected into the tail vein of mice. The proportion of CFSE positive cells in liver tissue was observed by the frozen section, and the proportion of labeled cells in the liver and spleen was tracked by flow cytometry. The expression of CD3, CD4, CD8, NK1.1, CD11b and Gr-1 in CFSE labeled adoptive cells was detected by flow cytometry. The intracellular lipid content of NKT cells in liver tissue was evaluated by Nile Red lipid staining. Results The injury of liver tissue and the levels of serum ALT and AST in MAFLD mice were significantly reduced. At the same time, liver immune cells up-regulated the expression of IL-4 and LDLR. LDLR knockout mice induced more severe MAFLD after giving MCD diet. Bone marrow adoptive cells had a significant therapeutic effect and differentiated more NKT cells to colonize the liver. At the same time, the intracellular lipids of these NKT cells increased significantly. Conclusion Bone marrow cell adoptive therapy can reduce liver injury in MAFLD mice by differentiating more NKT cells and increasing the intracellular lipid content of these cells.