Abstract: The effects of sludge-corn silage ratios (calculated as the COD_Cr, mass ratio is 1:0, 1:1, 2:1, 3:1) on the performance of two-phase anaerobic digestion (TPAD) under mesophilic condition, and the influences of solid retention time (SRT) on the steady-state characteristics of anaerobic digestion in methanogenic phase at the optimal sludge-corn silage ratio were investigated with methane yield and COD_Cr removal rates. The results showed that the performances of anaerobic digestion with corn silage were better than the control group, and the optimal ratio of sludge to corn silage was 2:1. Under this stable condition, the removal rate of COD_Cr in acidification phase was 17.5%, and the concentration of volatile fatty acid (VFA) was 752 mg/L; the removal rate of COD_Cr in methanogenic phase was 33.5%, the concentration of VFA was 250 mg/L, the biogas production was 47.7 mL/d. Therefore, the overall performances of the TPAD of the co-substrates was fruitful. When the optimal ratio of sludge to corn silage (2:1) was taken and the SRT of methanogenic reactor was set at 20 d, the methanogenic components changed in stable state were as follows:the removal rate of COD_Cr was 41.20%, the concentration of VFA was 238 mg/L, the biogas production was 51.3 mL/d, and the biogas yield was 8.4 mL/(d·g). The investigation indicated that the TPAD of the co-substrates under mesophilic condition had good performances when the ratio of sludge to corn silage was 2:1 and SRT was 20 d.