Abstract: Pyrolysis characteristics of oil sludge were studied by thermogravimetric analysis-Fourier transform infrared spectroscopy (TG-FTIR) and tubular electric furnace. The pyrolysis process and major influence factors like sludge property and heating rate were analyzed. The releasing behavior of noncondensed gas was also studied to understand pyrolysis mechanism. The results indicate that the pyrolysis process has five reactions including water volatilization, light oil volatilization, heavy oil pyrolysis, semicoke charring and mineral decomposition. Reaction of mineral oil focuses on 220℃～480℃. The source of sludge is important for its pyrolysis behavior. The weight loss of bottom sludge and sewage sludge is greater than that of petroleum contaminated soil. Property of oil source is less important relatively. mineral content was higher, volatile conversation rate increased; With the rising of heating rate the reaction rate increases, while volatiles conversion rate decreases. Pyrolysis mechanism includes cracking reaction of oxygenous functional groups, chain scission of linear and side chains of hydrocarbon, cyclization, aromatization and condensation reactions to dehydrogenate.