Interleukin–2 was observed via SABC, an immunohistochemical method, to investigate its expression and distribution in macaque’s spleen and its difference with sex. Positive cells within red pulp area in spleen of male macaque were strongly stained with cytoplasm with a medium density distribution. The majority of middle positive cells with a low-density distribution in white pulp area were stained with cytoplasm. The middle-density middle positive cells were distributed in the marginal region. The high-density of strong positive cells were found in the red pulp area of splenic cord in the spleen of female macaque, some nuclei were stained, while, others were stained with cytoplasm. Middle positive cells with nuclei stained had low-density distribution in the white pulp area. The middle-density middle positive cells were distributed in the marginal region. In short, the interleukin-2 in spleen of female macaque was apparently higher than that in males both on the number of positive cells and protein expression intensity (P<0.01 or 0.05). Higher expression of the interleukin–2 in red pulp area suggested that it played an important role in enhancing the humoral immune function, and this depended greatly on sex.