In recent years, the discovery of ovarian germ stem cells (OGSCs) has provided a new research direction for the treatment of ovarian failure. The ovarian microenvironment affects the proliferation and differentiation of OGSCs, and immune cells and related cytokines are important components of the microenvironment. However, whether improving the ovarian microenvironment can regulate the proliferation of OGSCs and remodel ovarian function has not been reported. In this study, we linked chitosan oligosaccharide(COS) with fluorescein isothiocyanate (FITC) to select the best route of administration. COS was given to mice through the best route of administration, and the changes in ovarian and immune function were observed using assays of organ index, follicular growth, serum estrogen (E 2 ) and anti-Mullerian hormone (AMH) levels, and the expression of IL-2 and TNF-α in the ovaries. COS significantly increased the weight of the ovary and immune organs, reduced the rate of follicular atresia, increased the levels of E 2 and AMH hormones, and increased the protein expression of IL-2 and TNF-α in the ovary. Then, COS and OGSCs were cocultured to observe the entry of COS into OGSCs and to measure the survival rate of OGSCs. With increasing time, COS gradually entered the cell, and the cytokines IL-2 and TNF-α significantly promoted OGSCs promotion. In conclusion, COS significantly improved the ovarian and immune function of mice with pathological ovarian aging, and improved the survival rate of OGSCs, which provided a preliminary blueprint for further exploring the mechanism of COS in anti ovarian aging.