Abstract: To develop the fermented food of Porphyra yezoensis, monascus and compound yeast and lactic acid bacteria were used to ferment Porphyra yezoensis. The active ingredients of Porphyra yezoensis during fermentation were determined, and their antioxidant, hypoglycemic and antihypertensive activities were evaluated. Results showed that the total phenol and flavonoid contents of M. purpureus fermented P. yezoensis (MF), M. purpureus and L. plantarum co-fermented P. yezoensis (MLF), M. purpureus and S. cerevisiae co-fermented P. yezoensis (MYF) significantly increased with fermentation time (P<0.05). The antioxidant activity was enhanced after fermentation. MYF had the highest ABTS⁺ free radical scavenging capacity and DPPH free radical scavenging capacity with trolox equivalents of (0.709±0.007) mg/g, (0.179±0.014) mg/g, respectively. MF showed the highest ferric reducing antioxidant power of (0.279±0.007) mg/g. MF exhibited the best hypoglycemic activity with the highest α-amylase and α-glucosidase inhibition values of 50.37%±0.73% and 69.42%±0.37%, respectively. The α-amylase and α-glucosidase inhibition values of MLF were 41.49%±0.51% and 39.60%±0.13%, whereas MYF had a lower hypoglycaemic activity of which the α-glucosidase inhibition capacity reached only 10.36%±0.45%. After fermentation, the antihypertensive activity was significantly enhanced (P<0.05) and the highest ACE inhibition rates were observed in MF, MYF and MLF with 83.21%±0.89%, 47.09%±0.27%, and 52.65%±0.64%, respectively. The results indicated that fermentation process could effectively promote the production of active substances and enhance the antioxidant, hypoglycemic, and antihypertensive activities of P. yezoensis. Among the three tested fermentation formula, MF exhibited the greatest improvement. This study provided theoretical basis for the potential application of fermentation technique in P. yezoensis food processing.