Objective: The aim of this study was to explore the digestive and fermentation properties of four economic red algae， including Gracilaria lemaneiformis， Bangia fusco-purpurea， Eucheuma muricatum and Porphyra haitanensis. Additionally， the anti-inflammatory potential of their fermentation products was evaluated， so as to provide evidences for the high value-added development of red algae. Methods: The changes of total carbohydrates， reducing sugars， proteins and total phenols in four red algae were determined by simulating oral and gastrointestinal digestion and colonic fermentation in vitro. The effects of red algae on intestinal microbiota were analyzed by Illumina MiSeq sequencing of 16S rRNA gene. The content of short-chain fatty acids in fermentation products was analyzed by high performance liquid chromatography. The anti-inflammatory activity of different fermentation products was evaluated by LPS-induced RAW264.7 cell model. Results: During in vitro simulated digestion， Porphyra haitanensis exhibited better bioavailability of carbohydrates， proteins and phenolics. The indigestible portion of these red algae reached the colon and were fermented by the intestinal microbiota. Porphyra haitanensis produced more short-chain fatty acids during fermentation， while all four red algae showed the ability to regulate the intestinal flora， increase the abundance of Bacteroidetes and decrease the ratio of Firmicutes/Bacteroidetes. All fermentation products exhibited significant inhibitory effect on LPS-induced inflammatory injury in RAW264.7 cells， and the Bangia fusco-purpurea fermentation product had a better inhibitory effect than others. Conclusion: Four red algae exhibited good bioaccessibility after in vitro simulated digestion. They were able to modulate the intestinal microbiota composition and showed potential anti-inflammatory activity. These results provided a basis for the development of high-value active products based on red algae.