AbstractThe development of antiaging functional products is a hot topic in the field of functional foods. However, the efficient extraction of functional ingredients is the limiting step for the functional food industry. Continuous phase‐transition extraction (CPE) is a new extraction technique that combines the advantages of Soxhlet extraction and supercritical extraction, which may have a distinct advantage over traditional methods in the extraction of flavonoids. In our study, the Box–Behnken design combined with response surface methodology was used to optimize CPE of crude flavonoids from finger citron fruit. The antiaging activities of finger citron crude flavonoids (FCCF) were evaluated by Caenorhabditis elegans (C. elegans) model. The optimal extraction conditions for CPE were as follows: ethanol concentration 85%, temperature 90°C, time 120 min, and pressure 0.2 MPa. Compared with the heat reflux extraction, the extraction rate and content of FCCF extracted by CPE increased by 24.28% and 33.22% (p < .05), respectively. FCCF extended the lifespan of C. elegans by 14.94% without causing adverse effects on their reproduction and locomotion ability. A further analysis suggested that FCCF prolonged the lifespan of nematodes under normal and oxidative stress by increasing the activity of major enzymes in endogenous antioxidant defense system and reducing the accumulation of reactive oxygen species (ROS) and malondialdehyde (MDA). The results confirmed the effectiveness of CPE in extracting crude flavonoids from finger citron fruit, and the extracted FCCF exhibited strong antiaging activities.