The low carbon emission and utilization of municipal sludge is an important guarantee for the construction of "waste free city" and coping with global climate change.  Chemical looping combustion/gasification technology can realize the sludge pyrolysis,combustion and carbon capture by looping of oxygen carrier between sludge fuel and air reactors.  The cheap and readily available iron - based oxygen carrier was used to carry out the chemical looping combustion of municipal sludge. In order to explore the pyrolysis mechanism of municipal sludge at the initial stage of chemical looping combustion based on the iron-based oxygen carrier,the X-ray optoelectronic energy spectroscopy,13C solid nuclear magnet and the proximate analysis,elemental analysis were used here to determine the type,the chemical valence state and bonding mode of the typical municipal sludge,so as to determine the chemical structure of molecular groups. Two structural models of sludge independent pyrolysis and oxygen carrier surface pyrolysis with AlFeO3 as oxygen carrier were constructed in this paper. The molecular dynamics simulations by the reaction force field (ReaxFF MD) is mainly simulated under the two influence factors of heating rate and pyrolysis temperature. The simulation results show that,under different heating rates,the products of sludge independent pyrolysis are mainly organic gas,and the too higher heating rate is not conducive to the pyrolysis of sludge molecular groups，16 K/ps is suitable. The increase of the pyrolysis temperature and the presence of the oxygen carrier both promote the pyrolysis of the sludge structure and reduce the generation of the tar oil. Without the oxygen carrier,the N mainly migrates into the heavy tar at different heating rates to participate in the subsequent combustion reaction.The pyrolysis temperature has little effect on the generation of the nitrogen-containing products. But the presence of Fe-based oxygen carrier promptes the generation of nitrogen-containing active groups,and then produces NO,while part of NO will be reduced into N2. The S elemental mainly migrates into the small molecular fragments or precipitates in the form of H2S.Therefore,iron based oxygen carriers improve the pyrolysis rate of solid fuels,and have a tendency to reduce the production of tar,reduce the generation of nitrogen oxides,but have little impact on sulfur dioxide emissions.