Abstract: Tween80 coupled with sodium hydroxide was used to promote the effect of sludge lysis. When the sludge lysis time was 15 min, the concentrations of protein and DNA in the supernatant were respectively 32.5 and 15.8 times higher than those in the initial supernatant. This indicated that the cell wall had been cracked and the intracellular protein and DNA had been extracted into the supernatant. Moreover, the concentrations of VFAs and NH₃-N increased with the increase of the concentration of Tween80 and time during the acidification of the sludge after lysis. The results showed that the addition of Tween80 could contribute significantly to the hydrolyzing effect of proteins and carbohydrates by acidification bacteria. After 24 h of acidification, the pH under different conditions was close to 7.4, and then the system went into a stable operation.