The resource utilization of protein in residual sludge is a research hotspot at home and abroad, and sludge pretreatment is an important way to realize protein release from sludge. In order to further improve the dissolution efficiency of protein in residual sludge, this paper selected thermal-alkali pretreatment, ultrasonic-alkali pretreatment and lysozyme pretreatment as the method of disintegration in sludge, and optimized the parameters with the protein extraction concentration as the main index. The isoelectric point method was also used to purify and recover crude protein. The results showed that the best cell disintegration effect was achieved by thermal-alkali pretreatment (pH=13, temperature 140oC, time 1.5 h). Protein extraction concentration reached at 2,062.98 mg?L-1 and the purification recovery rate reached at 62.42% under the optimal conditions. The obtained pretreatment conditions can provide a more precise technology reference for protein resource utilization.