Abstract: Effects of cow feces on anaerobic digestion process of Spartina alterniflora and the characteristics of anaerobic digestion with different ratios of cow feces and Spartina alterniflora were studied to promote biogas production. The results indicated that co-digestion meliorated the environment where microorganisms lived and increased the cumulative biogas production by 38.83%. Daily biogas production was stable and the peak was advanced for 13 days. When the ratio of Spartina alterniflora to cow feces was 3:1, the cumulative biogas production was the highest while the cumulative biogas productions of SC71(the ratio of Spartina alterniflora to cow feces of 7:1 on volatile solid), SC11(the ratio of Spartina alterniflora to cow feces of 1:1 on volatile solid), SC13(the ratio of Spartina alterniflora to cow feces of 1:3 on volatile solid) and SC17(the ratio of Spartina alterniflora to cow feces of 1:7 on volatile solid) were 92.99%, 79.00%, 73.59%and 61.17%, respectively. Co-digestion improved the buffer capacity. More cow feces caused a higher buffer capacity, and never accumulated organic acids. X-ray diffraction and Fourier transform infrared spectra of solid substances further proved that co-digestion promoted the utilization of as much as that of SC31 biodegradable substrates and the destruction of crystalline area of especially when the ratio of Spartina alterniflora to cow feces was 3:1.