Abstract: In order to clarify the composition and antioxidant activity of total flavonoids in Hibiscus syriacus petals, in this study, the total flavonoids and antioxidant capacity of Hibiscus syriacus petals were analyzed by liquid chromatography-mass spectrometry through DPPH and ABTS⁺ free radical scavenging experiments. The results showed that there were 9 flavonoids in Hibiscus syriacus petals, including apigenin-C-diglucoside, apigenin-7-O-rutoside, vitexin, kkaempferol-O-hexacarbose-C-hexacarboglycoside, sage phenol-7-O-glucosidee, kaempferol-3-O-malonyl, glucoside-7-O-glucoside, luteolin-7-O-glucoside, wheat flavone-O-malonyl-hexoside and luteolin-7-O-6-malonyl galactoside. H. syriacus of 'Red Heart', 'Purple French Cabaret', 'Red French Cabaret', 'Blueberry Smoothie' and 'Paeoniflorus' had good antioxidant properties. Taking the DPPH and ABTS⁺ free radical clearance rate as indicators, the equivalent Trolox equivalents were 35.51, 49.13, 50.28, 49.99, 49.34 mg Trolox/g (dry weight) and 20.23, 27.83, 44.11, 29.79, 35.53 mg Trolox/g (dry weight) respectively. The content of total flavonoids was the main factor affecting the antioxidant activity of Hibiscus syriacus flowers. Among the specific components, vitexin, kaempferol-O-hexose-C-hexoside, sage phenol-7-O-glucosidee and wheat flavone-O-malonyl-hexoside were the main total flavonoids affecting the antioxidant activity of Hibiscus syriacus flowers. This study showed that Hibiscus syriacus flower contained a variety of bioactive components and antioxidant capacity.