Abstract: To study the localization of estrogen receptor α (ERα) and its action in the process of reproduction during the different period of reproduction in goat ovary, supersensitive immunohistochemistry SP method was used to detect the distribution of the ERα immunoreactivity (ERα-ir) during the different period of reproduction in the goats ovary. The results showed that ERα-ir exist mainly in granulosa cells in the mature follicles, some granulosa cells in the developing follicle during oestrum and the trimester of pregnancy, cytoplasm of oocyte in primordiar follicle, cytoplasm of granular lutein cells and nucleus of theca lutein cells during the trimester of pregnancy, theca cells and cytoplasm of steroid secretory cells. The content of ERα-ir in granulosa cells in the developing follicle was few, only exist in the cytomembrane during the dioestrus. At the stage of primary follicle, the content of ERα-ir in oocyte was few. Later the content of ERα-ir was very abundant. The results suggest that ERα control the development of follicle, ovulation and pregnancy maintenance by activating different signal pathway. The above results provide morphological materials for research about the function of estrogen and estrogen receptor α in the ovary and its regulatory mechanism of reproduction.