Background <p>Oxidative stress (OS) is a significant challenge in the in vitro embryo culture of patients of advanced age. The Erzhi Tiangui (EZTG) formula has been shown to alleviate OS-induced apoptosis in granulosa cells (GCs) of patients undergoing in vitro fertilization (IVF) cycles. This study aimed to investigate the protective effects and underlying mechanisms of the EZTG formula on OS and apoptosis in GCs of patients with advanced age.</p> Methods <p>A total of 240 patients aged 35 to 42 years were randomly assigned to either the experimental group (EZTG formula) or the control group (placebo). The experimental group received 3&#xa0;g of EZTG formula three times daily, starting from the menstrual period preceding the IVF cycle for approximately 45 days, while the control group received a placebo. The primary outcome measure was the number of high-quality embryos, while secondary outcomes included additional indicators related to oocytes, embryos, and pregnancy outcomes. GCs were collected from advanced-age patients during oocyte retrieval. Nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) are key signaling molecules associated with OS prevention. These molecules potentially link the EZTG formula, OS mitigation, and embryo quality through Nrf2 activation. We examined the protein and mRNA levels of Nrf2/HO-1 and the activities of downstream antioxidant enzymes in GCs to elucidate the underlying mechanisms. Apoptosis-related protein and gene expression involved in the Nrf2/HO-1 signaling pathway were analyzed using Western blotting and quantitative reverse-transcription polymerase chain reaction (qPCR). Additionally, the active glutathione (GSH) levels in GCs were determined using enzyme-linked immunosorbent assay (ELISA).</p> Results <p>The number of high-quality embryos and fertilization rates were significantly increased in the EZTG group compared to the control group (both <i>P</i> &lt; 0.05). GCs from the EZTG group showed significant upregulation of GSH and adenosine triphosphate (ATP) levels (both <i>P</i> &lt; 0.05). Western blot and qPCR analyses indicated that the EZTG formula alleviated OS by activating the Nrf2/HO-1 signaling pathway. Specifically, the protein levels of Keap1, Bax, and Caspase-3 were decreased, while those of Nrf2, HO-1, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), and Bcl-2 were increased in the EZTG group compared to the control group (all <i>P</i> &lt; 0.05). Similarly, the mRNA levels of Keap1, Bax, and Caspase-3 were significantly decreased, while Nrf2, HO-1, and Bcl-2 were significantly increased in the EZTG group (all <i>P</i> &lt; 0.05). These findings suggest that the EZTG formula mitigates OS through the Nrf2/HO-1 signaling pathway, ultimately improving embryo quality in IVF-derived embryos.</p> Conclusion <p>The EZTG formula can improve embryo quality in patients of advanced age by activating the Nrf2/HO-1 signaling pathway, reducing OS and inhibiting GCs apoptosis. This study provides a scientific basis for the application of EZTG formula in improving IVF outcomes for patients of advanced maternal age.</p> Trial registration number <p><ExternalRef> <RefSource>www.chictr.org.cn</RefSource> <RefTarget Address="www.chictr.org.cn" TargetType="Other" /> </ExternalRef>, identifier ChiCTR2200065195. Registered on 31 October 2022.</p>