Objective To investigate whether the proportion of immune cells and related stem cells in the spleen of APP / PS1ΔE9 Alzheimer’s mice (AD mice) is different from that of normal mice. Methods The spleens of 9-month-old AD mice and their littermate normal control mice (six in each group) were collected. The ratio of CD4⁺T cells, CD8⁺T cells, B cells, monocytes, macrophages, and dendritic cells in the spleens of each group were detected by flow cytometry. At the same time, the ratio of cells with stem cell characteristics (C-kit⁺Sca-1⁺) among the above-mentioned cells was detected and compared. Results The AD mice showed significant differences in behavior compared with the control mice. However, there were no significant differences in the proportions of CD4⁺T cells, CD8⁺T cells, B cells, monocytes, macrophages, and dendritic cells in the spleens of AD mice compared with the control mice. The proportions of C-kit⁺Sca-1⁺cells in CD4⁺T cells, CD8⁺T cells, and B cells in the spleens of the AD mice were higher than those in the control mice, but because of individual differences, this was not statistically significant; the proportions of C-kit⁺Sca-1⁺cells in monocytes, macrophages, and dendritic cells were lower in AD mice than in the control mice. The difference between macrophages and dendritic cells was statistically significant. Conclusions Although the proportion of immune cells in the spleen of 9-month-old AD mice was not significantly different from that of normal control mice, in the myeloid cells of AD mice, the reserve of cells with stem cell characteristics was significantly lower than that of normal mice. Furthermore, compared with normal mice, the proportion of cells with stem cell characteristics among the lymphocytes was generally increased for AD mice. Taken together, these result indicated that AD mice had accelerated immune senescence compared with normal mice.