The health benefits of tea are primarily attributed to its chemical composition, particularly phenolic compounds. As a renowned tea from Guangdong, China, Xianhu tea (XHT) has not been thoroughly studied in terms of its phenolic composition or health-promoting properties. This study characterized the phenolic compounds in Xianhu tea water extract (XHT) using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and evaluated its antioxidant activity in vitro. Furthermore, the effects of XHT extracts on reactive oxygen species (ROS), malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), lipofuscin levels, and lifespan in