The kinetic mechanism of the co-combustion of sewage sludge (SS) and bituminous coal (BC) is studied. The separate combustion process of the SS can be divided into four stages, as follows: moisture precipitation, volatile precipitation, non-volatile substance precipitation, and fixed carbon burnout. During the co-combustion of the mixture, SS and BC maintained their respective combustion properties. The SS can significantly improve the ignition and combustion performance of BC. Through Fourier transform infrared spectroscopy analysis, we found that the main combustible component in the SS is the volatile organic matter, and the main emission product is CO2. These results provide a theoretical basis for the new technology of combined power generation of SS energy recycling.