Steam explosion technology can disrupt plant cell structures and release bioactive components, making it an important method for processing grain-based snack foods. To investigate the effects of steam explosion on the digestive properties of sea rice, samples were prepared under different steam explosion conditions (0.9-0, 1.0-0, 1.1-0, 0.9-2, 0.9-4) using steam explosion technology, with cooked sea rice as the control. The contents of rapidly digestible starch, slowly digestible starch, resistant starch, and the estimated glycemic index were determined by an in vitro enzymatic method. The INFOGEST standard in vitro digestion model was employed to measure the release of polyphenols and flavonoids, as well as the ferric reducing antioxidant power and oxygen radical absorbance capacity antioxidant activities. The results showed that, compared with the control group, the rapidly digestible starch content decreased by 15.9% and the resistant starch content increased by 21.7% in the steam explosion treatment groups. The estimated glycemic index value decreased with increasing pressure, reaching the lowest value of 39.32 in the 0.9-4 group (22.00% lower than that of the control). During INFOGEST digestion, the polyphenol release of the 1.1-0 group at 120 min of intestinal digestion was 5.42 times higher than that of the control group, and the flavonoid release was 2.38 times higher. Regarding antioxidant activity, the ferric reducing antioxidant power value of the 1.1-0 group was 3.08 times higher than that of the control group, and the oxygen radical absorbance capacity value was 2.93 times higher. In conclusion, steam explosion treatment can effectively improve the starch digestibility, reduce the estimated glycemic index, promote the digestive release of polyphenols and flavonoids, and enhance the antioxidant activity of sea rice, providing a theoretical reference for the development of nutritious convenience foods from sea rice.