Abstract: The essential oil from Calendula officinalis L. was extracted by microwave-assisted steam distillation. Taking the yield as the evaluation index, the extraction process of essential oil was optimized by orthogonal experiment on the basis of single factor test. The chemical composition of the essential oil was analyzed by gas chromatography-mass spectrometry (GC-MS). The antioxidant effect of the essential oil was evaluated by the scavenging activity of DPPH free radical, hydroxyl radical and ABTS⁺ free radical. The results showed that the optimum conditions for extracting the essential oil by microwave-assisted steam distillation were as follows: NaCl content 3%, ratio of material to liquid 1:30 g/mL, microwave power 240 W. Under these conditions, the yield of the essential oil was 0.156%. By GC-MS analysis, a total of 25 components were identified in the essential oil, accounting for 97.94% of the total components, mainly alcohols and terpenes. In the antioxidant test, the scavenging ability of the essential oil to DPPH free radical was weak. It had strong scavenging ability to hydroxyl radical and ABTS⁺ radical. In general, it had obvious antioxidant activity and a good dose-effect relationship. This study would provide more reliable technological parameters for large-scale production of Calendula officinalis L. essential oil, and provide basic data and reference for the evaluation of its antioxidant activity.