It is well reported that tumor cells can regulate host immune systems. To identify the detailed changes of immune cells between tumor bearing mice and normal mice, we evaluated the systemic immune cell phenotype of B16F10 tumor bearing mice in a time dependent manner. The lymphocytic population (CD4+ and CD8+ T cells) of tumor bearing mice significantly decreased compared to that of normal mice. We found that the Foxp3+CD25+ CD4 T cell decreased, but the Foxp3+CD25high CD4 T cell significantly increased. All subpopulations of CD8 T cells decreased, except the CD62L-CD44+ CD8 T cell subpopulation. The myeloid cell population (CD11b+ and Gr-1+ cells) of tumor bearing mice significantly increased. Specifically, Foxp3+CD25high CD4 T cell and CD11b+Gr-1+ cells significantly increased in early phase of tumor progression. These results are helpful to understand the change of the systemic immune cell subpopulation of tumor bearing mice in a time-dependent manner.