To optimize the extraction process of volatile oil from shade-dried Mentha haplocalyx Briq.leaves in Xuzhou using supercritical carbon dioxide extraction，and to conduct preliminary studies on its chemical composition and biological activity.Methods:Shade-dried M.haplocalyx leaves from Xuzhou were used as raw materials for supercritical carbon dioxide extraction of volatile oil.The extraction yield of M.haplocalyx volatile oil was used as the evaluation indicator.The factors affecting the extraction yield，including extraction pressure，temperature，and time，were investigated using single-factor experiments and the Box-Behnken design response surface methodology to select the optimal extraction conditions.Gas chromatography-mass spectrometry(GC-MS) was used to identify the structures of the separated compounds，and the relative content of the chemical components was determined by the peak area normalization method.The antioxidant and antimicrobial activities of the M.haplocalyx volatile oil were assessed through in vitro tests.Results:The optimal extraction conditions for M.haplocalyx volatile oil were found to be an extraction pressure of 26 MPa，extraction temperature of 51 ℃，and extraction time of 48.7 min.Under these conditions，the highest extraction yield of M.haplocalyx volatile oil reached 2.69%.The volatile oil contained 34 chemical components.Antioxidant and antimicrobial tests showed that the M.haplocalyx volatile oil from Xuzhou exhibited significant antibacterial activity against Escherichia coli，Bacillus subtilis，and Staphylococcus aureus，and demonstrated considerable scavenging effects on DPPH，ABTS+，and hydroxyl radicals.Conclusion:The extraction process has low operating temperature，no solvent residue，and high oil yield，making it suitable for the extraction of M.haplocalyx volatile oil from Xuzhou.The volatile oil has a complex chemical composition，excellent antioxidant and antimicrobial activities，and has broad application prospects.