In order to investigate the role of the lignin in the co-pyrolysis process of the sludge and the cellulose, the co-pyrolysis process was carried out in a thermogravimetry analyzer. The result shows that when the proportion of the sludge: cellulose: lignin was 1:1:0.4, the main co-pyrolysis temperature range was narrower, the ultimate pyrolysis weight loss was more, and the synergistic effect had a longer duration time. When the pyrolysis temperature was below 400 degrees C, the addition of the lignin could promote the copyrolysis process of the cellulose and the sludge, such as the decrease of the activation energy E.