Abstract: There is a certain degree of complementarity between municipal sludge and coal gangue in combustion properties, and both contain a large amount of heavy metal mercury pollutants. Therefore, it is necessary to study the migration and transformation characteristicsof mercury in the mixed combustion process. The occurrence forms of mercury in sludge and coal gangue samples, as well as the release characteristics of mercury during combustion were studied by chemical step extraction method, and the effects of temperature, mixingratio and atmosphere on the migration behavior of mercury in the samples were investigated. The results show that No.1 sludge is mainly composed of sulfate, carbonate and oxide-combined mercury and residual mercury. The content of residual mercury in No.2 sludge isthe highest. The main content of coal gangue is sulfide-bound mercury. The mercury released in the low temperature zone of sludge from200 ℃ to 390 ℃ is mainly organic and carbonate bonded mercury, while the mercury released in the high temperature zone from 390 ℃ to450 ℃ is mainly sulfide bonded mercury. The mercury released by gangue at low temperature ranging from 300 ℃ to 400 ℃ is mainly organic binding, carbonate binding and oxide binding states, while the mercury released at high temperature ranging from 400 ℃ to 600 ℃is mainly sulfide binding and some oxide binding states. The release of mercury in coal gangue at low temperature in advance is promoteddue to sludge mixing, and the promotion effect becomes stronger with the increase of sludge mixing rate. With the increase of oxygen content in the atmosphere, CO2 produced in the combustion process will be adsorbed on the surface of the particles and the heat transfer resistance is increased, thus inhibiting the release of organic-bound mercury and some carbonate-bound mercury in the mixture. Meanwhile, it is found that the effect of atmosphere on the release behavior of mercury in the high proportion of sludge mixture is weakened.