High solid anaerobic digestion (HSAD) of sewage sludge is one of the most efficient, effective, and environmentally sustainable remediation techniques; however, the presence of complex floc structures, hard cell walls, and large amounts of molecular organic matter in the sludge hinder HSAD hydrolysis. As a result, pre-treatment of sewage sludge is required to speed up hydrolysis and improve HSAD efficiency. Pretreatment approaches for enhancing sewage sludge HSAD are included in this review, which include mechanical, chemical, thermal, and biological procedures. The merits and disadvantages of various pretreatment processes, as well as their effectiveness, are explored, and recent advances for increased biogas production are reviewed.