Whether germline stem cells exist in postnatal female mammal ovaries has been disputed for more than one hundred years and not conclusive yet. In 2004, researchers found and isolated female germline stem cells (FGSCs) from postnatal mice, which challenged the viewpoint of existing nearly half a century that the bank of oocytes in ovaries will be never renewed in postnatal mammal female. And then a lot of researches not only pointed out that the de novo oocytes derived from FGSCs, but also found that if the FGSCs were delivered back into adult ovaries, they were capable of generating functional eggs produced healthy offsprings. However, some groups repeated or designed experiments carefully, but they did not get the same or even opposite results. Recently, some researchers announced that they had purified FGSCs from ovaries of reproductive-age women, which could produce functional oocytes in vivo and in vitro, but the fertilization competency of these oocytes still need to be clarified. Therefore, this paper reviews the study history of mammalian FGSCs, the long-standing controversy as well as prospects for the future use of these FGSCs.