Abstract: The appropriate extraction conditions of amaranthin (extractant, extraction time, extraction temperature and solid-liquid ratio) from Amaranthus tricolor L.by single factor experiment were determined.Response surface methodology was applied to optimize the extraction process, and then the antioxidant activity of amaranthin crude extract was studied.The results showed that the optimal conditions were as follows: solid-liquid ratio 1∶ 50 (m∶ v, g/m L) , extraction temperature 30 ℃ and extraction time 44 min with H₂O as extractant. Under these conditions, the predicted content of amaranthin was 0.308% with a relieve error of 0.98% when compared to the actual content, 0.305%. Thus, the optimized extraction conditions were reliable. In addition, there were obvious antioxidant activities in amaranthin, which the IC₅₀ value of DPPH, ·OH and O₂^-· free radical scavenging abilities were 0.18, 0.06, 0.35 mg/g, respectively.