Abstract: The objective of this work was to examine the effect of follicle-stimulating hormone (FSH) on the in vitro activation and viability of sheep primordial follicles. Sheep ovarian cortical fragments were cultured in a steel mesh culture system, various concentration of FSH (1, 10, 50, 100 ng·mL^-1) were either stabilized or dynamically (different days with different concentration of FSH) added in culture medium. Ovarian tissues, both fresh and cultured, were processed for histological and proliferating cell nuclear antigen (PCNA) assays, while tissue activity was evaluated by estrogen (E2) production during culture duration. As results showed, FSH of dynamic addition FSH started with up-grade dose (1-100 ng·mL^-1) followed by down-grade dose (100-1 ng·mL^-1), stimulated primordial follicle activation, survival, growth or granulosa cells proliferating, and also promoted the E2 production in tissues in vitro cultured, compared to other groups. The concentration of FSH with 50 ng·mL^-1 stimulated primordial follicle activation after 1 d culture, and in dose higher than 10 ng·mL^-1 of FSH groups stimulated follicle survival and growth. During culture duration, E2 production in all culture groups were increased constantly, which indicated that tissue activity were well maintained in the present study. In conclusion, this study suggestd that FSH involved in early follicle development and dynamic addition of FSH would benefit to primordial follicle developing and tissue activity maintenance.