Abstract: The n-hexane subcritical/supercritical extraction process of sludge was investigated.During the process,the organic matters were cracked,O,N and S in sludge were removed by reactions,and water on the sludge particle surface was efficiently separated.Simultaneously,the product distribution and characterization of extractives were analyzed.The results showed that the organic matters in sludge could be efficiently extracted by n-hexane under subcritical/supercritical conditions with the yield of n-hexane extractives up to 19.5%~24.2% (daf).The extractives can not be used directly as liquid fuels for combustion,but as raw materials for refining,owning to its low O content and high S and N contents.The organic matters in the aqueous phase are primarily composed of alcohols and carboxylic acids,which are suitable to be recycled as the solvent for the hydrothermal liquefaction of the residue from extraction.The organic matters in extracted residues which can be dissolved in tetrahydrofuran are up to 74.1%~84.9% (daf),which can be used to produce bio-oil by hydrothermal liquefaction.