Summary:To investigate the effect of cellulose on the anaerobic digestion gas production performance and microbial morphology of residual sludge, a semi continuous injection method was used at a temperature of 35 ℃± 1 ℃. The residual sludge and cellulose were subjected to combined anaerobic digestion according to the amount of organic matter (VS) added, i.e. VS sludge: VS cellulose=5:1, 2:1, 1:1. By monitoring and analyzing the daily gas production, stable methane content, methane production activity, and microbial morphology during anaerobic digestion process. The results indicate that the addition of cellulose can improve the nutritional balance of anaerobic digestion mixtures, which is beneficial for the progress of anaerobic digestion; The daily gas production of anaerobic digestion of sludge with three different amounts of cellulose addition was approximately 2.4 times, 4.8 times, and 9.2 times that of the control group (without cellulose addition), respectively; The proportion of CH4 in biogas was approximately 1.6 times, 2 times, and 2 times that of the control group, respectively; The methane production activities were 45 mL · g-1 VSS · d-1 (control group), 73 mL · g-1 VSS · d-1, 94 mL · g-1 VSS · d-1, and 120 mL · g-1 VSS · d-1, respectively. The microorganisms in the stable anaerobic digestion sludge are mainly composed of spherical bacteria, rod-shaped bacteria, and filamentous bacteria. The addition of cellulose can improve the mixed and uneven distribution of different bacterial colonies in the control group, and promote the growth of the same bacterial colony. Among them, in the addition ratio of VS sludge: VS cellulose=1:1, the number of filamentous bacterial colonies is large. In the other two addition ratios, the microorganisms in the stable period are mainly spherical and rod-shaped, but the number of spherical bacteria is higher in the addition ratio of VS sludge: VS cellulose=2:1.