To observe the effects of PI3K agonist on the expression of PI3K/Akt/Foxo3a protein levels, cell cycle, and apoptosis protein of ovary of newborn rats. Methods: The ovaries of female rats of aged in 7 days (7d) were cultured in vitro and were randomly divided into control group (the ovaries of the rats were cultured without PI3K activator or PI3K pathway inhibitor for 7d), group A (the ovaries of the rats were cultured by PI3K activator for 7d), and group B (the ovaries of the rats were cultured by PI3K pathway inhibitor for 7d). The follicular morphology of ovarian tissue cultured for 5d was observed by HE staining, and the apoptosis of ovarian cells was detected by fluorescence microscope method. Western blot was used to compare the protein expressions of P-Akt, P-Foxo3a, CDK2, P27, Bcl-2, and TAP63, and PCR was used to detect the mRNA expressions of PI3K, Akt, Foxo3a, Bcl-2, p27, Cdk2, and Tap63 in the ovarian tissues on the 3rd d, 5th d, and 7th d after culture. Results：The protein expressions of PI3K, p-AKT, p-FOXO3A, BCL-2, CDK2, and TAP63 in the ovarian tissues of the rats in group A had increased significantly (P<0.01), especially on the 5th day after culture (P<0.05), but then which had decreased gradually after the 7th day after culture (P<0.05). The protein expression of P27 protein of the rats in group A had decreased significantly. The protein expressions of PI3K, p-AKT, p-FOXO3A, BCL-2, CDK2, and TAP63 in ovarian tissues of the rats in group B had increased significantly (P<0.01), but the protein expression of P27 protein of the rats had decreased significantly. Conclusion: Activation of PI3K/AKT/Foxo3a signaling pathway can promote the development of primitive follicles, and the mechanism of which may be related to the up-regulation of the protein expression of PI3K, AKT, FOXO3A, BCL-2, CDK2, and TAP63 in ovarian tissues, and related to the down-regulation of the expression of P27 protein.