The influence of extraction solvent, pH and the extraction conditions on the extraction ratio of anthocyanin from purple sweet potato was optimized by single experiment and 2-level factorial design. By using 2⁴ factorial design, the extraction time and temperature were identified as main factors, and the selected variables were further investigated by steepest ascent analysis and optimized by central composite design. The results indicated that hydrochloric acid with ethanol solution was the best solvent, meanwhile, the extraction temperature and time showed a higher influence to the extracting ratio. The optimized extraction ratio was obtained after 74 ℃ and 84 min, leading to the extraction ratio of 419.529 mg/100 g.