Abstract: Taking municipal sludge from sewage treatment plants as the research object, the study investigated the ease of reduction of different iron sources, γ-FeOOH,Fe₂O₃,and α-FeOOH,by dissimilatory metal-reducing bacteria（DMRB） during anaerobic treatment of sludge, as well as the impact of acid-base+ultrasonic combined pretreatment on the release of phosphorus from sludge and the promotion of the formation of blue iron ore.The results showed that the reduction rates of iron in different iron source systems were: γ-FeOOH（68.28%）,α-FeOOH（20.92%）,and Fe₂O₃（5.32%）.The difficulty of iron reduction may be most affected by the crystallinity of the iron source, with lower crystallinity being more easily utilized by microorganisms.Both acid/alkali and ultrasonic pretreatment can effectively promote the release of phosphorus.Under the same ultrasonic conditions, the phosphorus release performance in alkaline environment is significantly better than that in acidic environment.The release of PO₄^3- under initial pH=9 and 11 conditions increase by 68% and 80% respectively compared to neutral conditions.In addition, a neutral to alkaline environment is also beneficial to the dissimilatory iron reduction process of DMRB,which facilitates the binding of phosphorus released from the system with reduced iron, thereby promoting the formation of vivianite.Compared to the anaerobic fermentation system alone, the pretreatment combined with anaerobic fermentation system increased the release of PO₄^3- by 94% and the production of vivianite by 110%.