Effects of cow feces on anaerobic digestion process of Spartina alterniflora was studied by batch model at 35 degrees C. When Spartina alterniflora was digested alone, the biogas yield was 222.61 mL/g, and it was acidified from 10 d to 15 d. When cow feces was added, the environment where microorganisms lived in was meliorated, pH value was stabilized and biogas production was improved by 38.83%. Volatile fatty acids production was not affected significantly, but the peak was advanced. FTIR and XRD analysis of solid residue substances further proved that co-digestion promoted the removal of carbohydrates and resulted in higher content of lignin than Spartina alterniflora straw digested alone, and promoted the destruction of crystalline of cellulose. The crystallinity index (C(x)I) of Spartina alterniflora, digested Spartina alterniflora and co-digested Spartina alterniflora were 0.617 6, 0.6200 and 0.615 4, respectively. Therefore, adding cow feces was beneficial for the decomposition and increasing the biotransformation rate of Spartina alterniflora straw.