Abstract: This study aimed to investigate the optimal extraction process for polyphenols from Camellia nitidissima Chi and to analyze the total polyphenol composition and antioxidant activities both in vivo and in vitro post-purification. In this study, using Camellia nitidissima Chi as the raw material, we screened for the optimal extraction parameters of ultrasonic power, extraction temperature, ethanol concentration, and material-liquid ratio based on single-factor experiments. A response surface methodology was then designed to refine these parameters. The results indicated that the optimal conditions were an ultrasonic power of 290 W, an extraction temperature of 35 ℃, an ethanol concentration of 55%, and a material-liquid ratio of 1:30 g/mL. Under these conditions, the yield of polyphenols from Camellia nitidissima Chi was 3.53% .The extract was purified using Lx-8 type macroporous resin, achieving a tea polyphenol purity of 63.73%. High-Performance Liquid Chromatography (HPLC) was utilized for both qualitative and quantitative assessments of five specific polyphenol monomers. This analysis determined the concentrations of gallic acid, chlorogenic acid, epicatechin, rutin, and ellagic acid to be 0.47, 11.18, 59.03, 18.34, and 16.41 mg/g, respectively. In addition, the polyphenols extracted from Camellia nitidissima Chi demonstrated a significant ability to boost oxidative damage resistance in C. elegans. This was evidenced by a marked increase in SOD (superoxide dismutase) enzyme activity and a decrease in MDA (malondialdehyde) levels within the C. elegans specimens.