Based on the single factors, the response surface tests were used to optimize the process conditions of low-sugar yeast fermentation of the purple sweet potato to prepare high antioxidant activity powder, and the changes of total flavonoids, total phenols, anthocyanins and antioxidant capacity before and after fermentation were investigated. The optimum fermented conditions were determined as follows: 0.95% yeast addition, 10：22 (g/mL) ratio of feed to liquid, fermentation at 23 ℃ for 16 h. The antioxidant capacity was 404.94 mg VCEAC/100 g, with a total phenol content of 123.85 mg GAE/100 g, a total flavonoid content of 610.64 mg rutin/100 g, and a anthocyanin content of 26.99 mg/100 g. The fermented purple sweet potato powder had certain antioxidant capacity, and the stability of anthocyanins was better than that of its unfermented powder.