Angelica sinensis is well documented as a traditional medicine for a broad spectrum of disease. Recently, supercritical carbon dioxide extraction has been developed as an emerging green technology for processing of Angelica sinensis essential oil (AEO). To investigate the volatile components and antioxidant activity of AEO both in vitro and in vivo, we conducted an analysis of its chemical composition using gas chromatography-mass spectrometry (GC-MS). The results showed that AEO was mainly composed of phthalides, such as (Z)-Ligustilide (12.85%), 2,4-di-tert-butylphenol (11.6%), and 3-Butylidenephthalide (3.16%). In vitro antioxidant experiments indicated that when the concentration of Vitamin C was 10 μg/mL, the scavenging capacity of 1,1-diphenyl-2picrylhydrazyl (DPPH) and 2,2-azino-bis-3-ethyl-benzothiazoline-6-sulfonic acid (ABTS) for free radicals approached 100%, while the required AEO concentrations were 0.5 mg/mL and 0.2 mg/mL, respectively. Additionally, the iron-reducing capacity also showed a concentration-dependent relationship with AEO. In vivo experiments showed that Saccharomyces cerevisiae was cytotoxic after treatment with AEO at concentrations greater than 0.2 mg/mL. Furthermore, in a model of oxidative stress under 2 mM hydrogen peroxide (H₂O₂) stress, AEO increased the resistance of yeast to H₂O₂-promoted oxidative stress and improved its survival rate. These results demonstrate that AEO has good antioxidant capacity, and we hope to actively expand the application of AEO in various fields to fully develop and utilize this plant resource.