Background: To explore the molecular pharmacological mechanism of (-)-Epicatechin (EC) on the treatment of premature ovarian insufficiency (POI) by network pharmacology method and in vitro experiments. Methods: Relevant potential targets for EC were obtained based on Traditional Chinese Medicine System Pharmacology Database (TCMSP), a bioinformatics analysis tool for molecular mechanism of Traditional Chinese Medicine (BATMAN-TCM) and STITCH databases. The OMIM and GeneCards database were utilized to screen the known POI-related targets, while Cytoscape software was used for network construction and visualization. Then, the Gene Ontology (GO) and Pathway enrichment analysis were carried by the David database. Furthermore, KGN cells were performed to validate the predicted results in oxidative stress (OS) model, and antioxidant effect was examined. Results: A total of 70 potential common targets for EC in the treatment of POI were obtained through network pharmacology. Metabolic process, response to stimulus and antioxidant activity occupied a leading position of GO enrichment. KEGG analysis indicated that PI3K/AKT, TNF, estrogen, VEGF and MAPK signaling pathways were significantly enriched. In addition, cell experiments showed that EC exhibited antioxidant effects in an H2O2-mediated OS model in ovarian granulosa cells by regulating the expression of PI3K/AKT/Nrf2 signaling pathway and multiple downstream antioxidant enzymes.  Conclusion: EC could regulate multiple signaling pathways and several biological processes. EC had the ability to downregulate elevated OS level through the PI3K/AKT/Nrf2 signaling pathway and represented a potential novel treatment for POI.