Abstract: Smoldering is a new type of low calorific value organic solid waste heat treatment technology. According to the characteristics of sludge smoldering ash,the self-sustaining smoldering test ofsewage sludge( SS) was carried out to provide technical support for the promotion of smoldering disposal technology of SS. Based on a lab-scaled smouldering reactor,self-sustaining smoudering of SS was achieved with parameters of 50% water content of SS,3.5 cm/s of air Darcy flow rate,( wet) SS and sand mixing ratio of 1 ∶ 4. The process characteristics of SS self-sustaining smoldering treatment were analyzed by smoldering temperature curve. The mass lose profile was also calculated based on the temperature records and the basic properties of the raw SS. To compare with combustion and pryolysis,the SS was also sent to burn at 1 000 ℃ and pryolyzed at 500 ℃,followed by collection of the smouldering ash( ASH-1),combustion ash( ASH-2),and pryolysis produced char( CHAR). BCR sequential extraction method was then applied to study the occurrence forms of major elements( Na、K、Mg、Ca、Al、Fe、P) and trace elements( Zn,as,Cr,Cd,Pb,Ni,Cu) in the three residue samples. The study shows that the smouldering treatment can be divided into four periods: preheating,ignition,self-sustaining smouldering,and extinguishing; the highest temperature is678 ℃ of the bottom material combustion peak temperature in the ignition stage,and and the average temperature of the self-sustaining smoldering process is 517 ℃ . The median moving rate of burning front is 0.37 cm/min,and the average mass losing rate is 10.41 g/min during self-sustaining smouldering; the dominating mineral element in ASH-1,ASH-2,and CHAR,is Si,and the main trace elements are Zn,Pb,and Cr; Na,K,Al,Fe,P,and As、Cr、Cd、Pb in the three residues are dominated in residue form; the content of acid soluble form of Na,K,Mg,Ca,and Zn,As,Ni in ASH-1 are higher than those in ASH-2 and CHAR. Therefore,the further disposal of ASH-1,ASH-2,and CHAR in practice should take the differences of the occurrence forms of the inorganic elements into consideration.