To screen for water lily cultivars with high flavonoid content and excellent antioxidant performance and provide data support for the research and development of high value-added products of water lilies, the flower color, total flavonoid and phenol content, water content, and pH values of 10 water lily cultivars as well as antioxidant activity of their extracts were comprehensively analyzed. Petals of the Nymphaea “Eldorado” and Nymphaea “Purple Joy” contained the most total flavonoids (20.40 mg•g-1) and total phenols (31.22 mg•g-1), respectively. The total phenol contents of all individual cultivars were significantly higher than their total flavonoids. Significant positive correlations were observed between total flavonoid content and brightness L* (R=0.652) and color phase b* (R=0.645) (P<0.05), whereas a significant negative correlation with color phase a* (R=-0.733) (P<0.05) was identified. The total phenol content displayed no significant correlation with flower color parameters. Analysis using the DPPH method demonstrated that the Nymphaea “Red Flare” petals flavonoid extract exhibited the best scavenging ability, with an EC50 of 2.51 μg•mL-1, followed by the Nymphaea “Doris Holt” cultivars, which demonstrated an EC50 of 4.51 μg•mL-1, and then by Vc. Nymphaea “Zi Beike” petals flavonoid extract showed the highest scavenging ability in the ABTS method, with an EC50 of 24.31 μg•mL-1 and also exhibited outstanding performance in the Ferric Reducing Antioxidant Power method, where Vc displayed the strongest scavenging ability. These findings collectively demonstrate that water lily petals are typically rich in flavonoids and phenols and exhibit excellent antioxidant activity. Notably, the Nymphaea “Red Flare” and Nymphaea “Doris Holt” cultivars stand out in DPPH free radical scavenging, ultimately showing great potential as high-quality natural antioxidants. Furthermore, these findings provide crucial theoretical foundations and data support for targeted utilization of water lily resources in high-value-added products such as health supplements and cosmetics.