Abstract: In order to explore the flavor substances and its antioxidant capacity in the light-flavor, strong-flavor and sauce-flavor Baijiu, the HS-SPME/GC-MS was used to determine and analyze the flavor substances in four kinds of Baijiu in the market. 41 and 28 kinds of flavor substances were detected in two kinds of strong-flavor Baijiu (Nong1, Nong2), 41 kinds of flavor substances were detected insauce-flavor Baijiu (Jiang), while only 11 kinds of flavor substances were detected in light-flavor Baijiu (Qing). Among them, the most important flavor ingredient was esters, with a quantity of up to 30, and the content of ethyl acetate, ethyl butyrate, ethyl lactate and ethyl caproate in esters was higher than other esters.In addition, the method of ultrasound treatment was used for extracting substances in Baijiu. The antioxidant capacities of the four kinds of Baijiu were analyzed. Among them, the DPPH free radical and superoxide anion scavenging ability of Nong1 was stronger, and the scavenging rate was 41.87% and 38.46%, respectively. The hydroxyl free radical scavenging ability of Nong2 reached 46.98%. The hydroxyl free radical scavenging ability and ABTS free radical scavenging ability of Jiang were more outstanding, which was 48.00% and 31.50%, respectively. On the other hand, Qing had a certain ability to remove several kinds of free radicals such as DPPH(22.91%), hydroxyl radical (31.93%), ABTS (23.41%) and superoxide anion (17.20%).In general, these 4 kinds of Baijiu had a certain antioxidant capacity.