Differences of nutrient content, polyphenol profile and antioxidant activity of quinoa were explored from different grains quinoa of Qingbaili 1 (white grain), Gongza 4 (red grain) and Qingli 2 (black grain). Results showed that there were significant differences in nutritional quality among the three kinds of quinoa (P＜0.05), among them, crude protein content of white quinoa, fat and starch content of red quinoa, and crude fiber, ash and total amino acid content of black quinoa was the highest, respectively. Main type of quinoa pholyphenols was free form and their contents were significantly different (P＜0.05), with the contents of free phenol and bound phenol followed black＞red＞white and less flavonoids. A total of 19 phenols were detected, among them p-coumaric acid was the most abundant and gallic acid was not detected. DPPH·scavenging ability of different quinoa’s bound phenols was stronger, ABTS⁺· scavenging ability and FRAP of black quinoa bound phenols, white and red free phenols were stronger, and the black quinoa had the relatively strongest antioxidant activity. Quinoa crude fiber and protein were significantly correlated with free phenols, flavonoids and their bound FRAP and ABTS⁺· scavenging power, and it could be used to assess the content of quinoa polyphenols as well as the level of antioxidant activity.