〔Abstract〕 Objective To establish myeloid(including macrophage and granulocyte) specific knockout mice of mammalian sterile line 20-like kinase 1(MST1) gene for furtherinvestigating the role and the mechanism of MST1 in macrophages in related clinical diseases. Methods Mst1 flox / flox LysM-Cre(referred to asMst1 ΔM / ΔM hereafter) mice were generated by crossingMst1 flox / flox with lysozyme(Lysm-Cre) mice. The loxP site and Cre gene were amplified by PCR for genotyping.The knockdown efficiency of MST1 in macrophages was verified by quantitative PCR and immunofluorescence.The main immune cell populations in the livers were detected by flow cytometry. Results Mst1 flox / flox LysM-Cre(Mst1 ΔM / ΔM ) was the genotype of macrophage specific knockout MST1 mice.The results of qPCR and immunofluorescence showed that the knock-out efficiency of MST1 was more than 70% in bone marrow-derived macrophages and peritoneal macrophages.Flow cytometry showed that macrophage knockout of MST1 had no significant effect on the main immune cell populations in the liver of mice. Conclusion Macrophage-specific knockout of MST1 mouse model is successfully established, which lays a foundation for further investigation on the role and mechanism of macrophage MST1 in clinical related disease.