Abstract: In order to explore the optimum extraction process of polysaccharide and antioxidant activity in vitro in black corn kernel. In this study, black corn kernel was used as raw material, ultrasonic-assisted extraction was applied to extract polysaccharides from black corn kernel. To explore the effects of ultrasonic power, solid-liquid ratio, extraction time, temperature and frequency on the yield of polysaccharide. The extraction process of polysaccharide from black corn kernel was optimized by response surface methodology. Besides, the antioxidant activity of the polysaccharide was investigated by measuring its scavenging ability on DPPH·, ABTS⁺·, and ·OH. The results showed that the extraction yield of polysaccharide from black corn kernel could reach up to 41.09%±0.59%, in these conditions: The solid-liquid ratio was 1:20 g/mL, the extraction temperature was 74 ℃, the extraction time was 60 min and the extraction frequency was 3 times. The IC₅₀ values of scavenging rates on DPPH·, ABTS⁺· and ·OH were 1.959, 1.529 and 0.3554 mg/mL, respectively. Moreover, the scavenging rates showed a certain dose-effect relationship with the sample concentration, indicating that the polysaccharide had a strong antioxidant activity, thus providing a theoretical basis for further research and utilization.