Objective To study the diversities of expression of estradiol receptor β（ERβ）in the ovary of mice and pigs. Methods Immunohistochemistry was used in the present study in order to detect the expression and distribution of estradiol receptor β in tissue section taken from both the mouse and pig. Results In the ovary of mouse, there was a higher intensity of immunohistochemical staining for ERβ in the corpora lutea and the cytoplasm of oocytes in all sizes of growth follicles, and a weaker intensity of immunohistochemical staining for ERβ in the granulose cells and thecal cells in all sizes of follicle. In addition, there was also a weaker intensity of immunohistochemical staining for ERβ in the interstitial cells and germinal epithelium. In the ovary of pig, there were highly intensity of immunohistochemical staining of ERβ in the thecal cells of follicles. Staining was also detected in the granulose cells in the follicles before the formation of an antrum, but some of the granulose cells in the antrum follicle expressed ERβ, at the same time the others did not expressed it. There was no obvious expression in the interstitial cells or germinal epithelium. Conclusion There are great differences in the expression and distr