There have been a great deal of interest to dispose sludge through the combustion technology. The water content of sludge has a critical effect on its combustion and it is important to study the combustion mechanism of dewatered sludge. In addition, pyrolysis is regarded as the initial step of the whole combustion of solid fuels such as coal, sludge, RDF (Refuse Derived Fuel) and et. al. So it is necessary to investigate pyrolysis behavior of sludge in order to deeply investigate its combustion behavior. This paper presents the pyrolysis and combustion behaviors of sewage sludge and paper-making sludge. Tests were carried out using WCT-2 thermal balance which can perform experiments such as TG, DTG and DTA at the same time. The primary constituents and heating value of aforementioned sludges were also analyzed. Based on the TG data of sludge, kinetics parameters of combustion of sludge were obtained. The results indicate that the different sludge has distinctive kinetic parameters.