The effects of thermostable α-amylase, cellulase, and complex enzyme coupled with extrusion on the polyphenols and antioxidant activity of sea rice were investigated. Sea rice powder was sprayed evenly with the test enzymes or complex enzyme (mixture of both enzymes in equal amounts) at a concentration of 100 or 1 000 U•g-1 and processed using a twin-screw extruder. Changes in free and bound phenolic, flavonoid, and anthocyanin contents and antioxidant activity of sea rice were analyzed. Compared with the control group (direct extrusion of sea rice without enzyme addition), extruded sea rice hydrolyzed with 100 or 1 000 U•g-1 thermostable α-amylase or the complex enzyme exhibited elevated free phenolic content (from 95.60 mg gallic acid equivalents (GAE)/100 g dry weight (DW) to 110.38, 176.33, 108.51, and 195.65 mg GAE/100 g DW), elevated free flavonoid content (from 50.42 mg catechin equivalents (CE)/100 g DW to 53.00, 100.38, 58.76 and 107.59 mg CE/100 g DW), elevated anthocyanin content (from 5.18 μg chlorogenic acid equivalents (CGE)/g DW to 5.84, 7.18, 5.51 and 9.85 μg CGE/g DW), elevated ferric reducing antioxidant power (FRAP) (from 728.21 μmol Fe2+/100 g DW to 754.33, 882.4, 764.77 and 929.72 μmol Fe2+/100 g DW), and elevated oxygen radical absorbance capacity (ORAC) (from 1 501.56 μmol Trolox equivalents (TE)/g DW to 1 872.74; 1 925.24; 1 826.8; and 2 201.48 μmol TE/g DW). In contrast, cellulase addition did not significantly affect phenolic and flavonoid release. However, free phenolic, free flavonoid, and anthocyanin contents increased the most with the addition of 1 000 U•g-1 complex enzyme coupled with extrusion; its antioxidant capacity was also significantly higher than that of the other groups. This study aimed to broaden the scope of deep processing and utilization of sea rice and to provide a theoretical basis for the development of sea ricebased nutritional replacement meals.