To investigate the effect of SO₃ gas pre-treatment on the extraction yield of Atractylodis Macrocephalae Rhizoma essential oil and polysaccharides, as well as the quality, single factor experiments and response surface methodology were used to optimize the pre-treatment process, GC-MS was used to analyze the changes in the chemical composition of the essential oil, and antioxidant experiments were used to evaluate the changes in the biological activity of the essential oil and polysaccharides. The results showed that the optimal pre-treatment conditions were: SO₃ dosage of 2.0%, 47 ℃, and pre-treatment time 58 min. At this time, the extraction yield of essential oils and polysaccharides increased by 27.5% and 29.9%, respectively. The results of essential oil extraction kinetics showed that the extraction efficiency was significantly improved after pre-treatment. The scanning electron microscope (SEM) results showed that many pores appeared on the surface of Atractylodis Macrocephalae Rhizoma after pre-treatment, which confirmed that pre-treatment could contribute to extract essential oils and polysaccharides. GM-MS analysis showed that pre-treatment only had slight effect on the chemical composition of Atractylodis Macrocephalae Rhizoma essential oil. Essential oils only have little effect on DPPH and ABTS radical scavenging ability, which was consistent with the results of GC-MS analysis. In addition, pre-treatment had no significant effect on the ABTS free radical scavenging ability of polysaccharides. These results indicated that SO₃ gas pre-treatment could significantly improve the extraction efficiency of Atractylodis Macrocephalae Rhizoma essential oil and polysaccharides, had no obvious effect on their biological activity, and could be used to extract Atractylodis Macrocephalae Rhizoma essential oil and polysaccharides.