The remaining sludge is a semi-solid by-product generated in the sewage treatment process (with a water content of over 80%), of which bound water and intracellular water are the difficulties in sludge dewatering, accounting for about 75% of the total moisture. The properties of carrying a large amount of negative charge, strong hydrophilicity, and high compressibility make it a bottleneck in sludge dewatering. This article elaborates on the mechanisms of pretreating residual sludge using physical, chemical, and biological methods, summarizes the problems existing in various enhanced dewatering methods, and the effects of various conditioning agents on enhancing sludge dewatering. The new type of conditioning agent, propane hydrate, has the dual advantages of enhancing dewatering and recycling. The combination of various conditioning agents has a stronger effect on enhancing the deep dewatering of residual sludge. Comparing with commonly used mechanical dewatering equipment, the selection basis of mechanical dewatering equipment is summarized. The residual sludge contains abundant biomass resources, and resource utilization is a promising disposal method. The article summarizes the post-treatment disposal methods and resource utilization pathways for deep dewatered residual sludge, and prospects for future research directions, providing reference for the resource utilization of residual sludge.