Some charaterasics of female fetal reproductive system were studied in different gestation phases of Chinese northeast fine-wool sheep. The results showed that reproductive system consisted of ovary, oviduct, uterus and genitalia. The fetal ovaries were granular in early phase and became elliptic in later phase. The functional formula of ovarian weight, length and volume was obtained.Primary oocyte was encapsulated by monolayer cells in 7-week fetal ovary cortex. Primordial follicles were formed in 8-week fetal ovary, the follicular cells were sporadically arranged and not always regular. Complete organization of primordial follicles appeared until 10-week gestation, most of them scattered in nests in the following weeks of gestation. Two types of follicular complexes were found in fetal. There were continuous and quick mitosis of oogonia in fetal ovaries, large complexes were formed by oogoniaes encapsulated by multilayer of follicular cells, then they differentiated into small complexes, one or more primary oocytes were formed by mitosis of oogonia, primordial follicles which were caused by follicular cell approaching into them developed.