Abstract: The disruption of excess sludge is an effective means to improve its utilization rate. In this study, the effects of four pretreatment methods on sludge disruption rate were investigated by single factor test. Then the disruption effect of combined pretreatment was compared, and the best combined pretreatment method was determined. The morphological changes of excess sludge before and after disruption were observed by optical microscope. Finally, the change of sludge particle size was measured by laser particle size analyzer. The results showed that ultrasonic pretreatment had the best effect on sludge disruption among ultrasonic, thermal hydrolysis, surfactant and complex enzyme pretreatment. The sludge disruption rate was 18.1% under 0.15 W/mL energy density and 10.0 min ultrasonic time. The effect of surfactant pretreatment on sludge disruption was the worst, and the sludge disruption rate was only 8.5% at 60 mg/gTS addition. Compared with the single pretreatment, the surfactant combined with ultrasonic pretreatment showed a synergistic effect. The sludge disruption rate increased by 9.0 %, and the sludge particle size decreased by 45.5%~67.9%.