Objective PSGL-1 is specifically expressed in leucocytes. The aim of this study was to explore the changes of myeloid-derived suppressor cells (MDSCs) in the spleen and bone marrow in PSGL-1-deficient mice. Methods PSGL-1^-/- mice were used in the experiment. After identification of the offsprings, flow cytometry was used to test the expression of CD11b and Gr-1 in C57 and PSGL-1^-/- mice. Results Compared with the C57 mice, the expression of MDSCs was up-regulated in the PSGL-1-deficient mice (P<0.001). Conclusion The expression of MDSCs is upregulated in PSGl-1-deficient mice.