In the context of the accelerating aging population and the continuous decline in birth rates nationwide, delaying reproductive aging in women and protecting the fertility of women of childbearing age have become urgent issues and key demands that need to be addressed in the field of maternal and child health in China. The ovaries have reproductive and hormone secretion functions and are crucial throughout the female reproductive lifecycle. Women of childbearing age in China face a serious problem of diminished ovarian reserve (DOR), which can lead to infertility, failed in vitro fertilization (IVF) treatments, miscarriage, and other adverse pregnancy outcomes, severely affecting the safety of women and their offspring. For DOR patients who desire to conceive, failure to intervene and treat promptly can result in irreversible losses and impose a significant psychological burden on them. However, there are currently no clear and reliable interventions that can improve ovarian function and enhance fertility in women with DOR. Therefore, exploring new, safe, and patient-acceptable intervention strategies is urgently needed, as it may bring hope and light to women with DOR. Nutrient supplementation, especially vitamin supplementation, has received increasing attention in disease treatment due to its safety, bioavailability, and effectiveness. Previous studies have shown that vitamin C may play an important role in treating diminished ovarian reserve. However, its effects on ovarian function need to be validated in the population. Based on the above research background, this project will conduct a randomized, placebo-controlled, double-blind, multicenter trial. The study subjects will be DOR infertility patients undergoing IVF/ICSI treatment. The intervention group will receive oral vitamin C supplementation at a dosage of 500 mg per dose, twice a day; the control group will receive a placebo with the same dosage and method for at least three months. Patients will be followed up until delivery outcomes, comparing the IVF/ICSI treatment results between the vitamin C supplementation group and the placebo group. The primary endpoint of this clinical trial is the live birth rate of the IVF/ICSI treatment cycle. Secondary endpoints include indicators of improved ovarian reserve function, ovarian aging molecular clocks, IVF-embryo culture indicators, pregnancy rates, pregnancy complications, and neonatal conditions, thereby providing new clues and theoretical basis for clinical treatment plans for DOR patients.