Oil sludge (OS) is a typical hazardous waste from the petrochemical industry. Currently, the increasing ratio of high-sulfur crude oil worldwide that results in the growth production of OS with high sulfur content has drawn much attention. OS incineration with calcium-based additives has great potential to be an efficient and clean approach for the large-scale treatment of high-sulfur-containing OS. In this work, the migration characteristics of sulfur and nitrogen during OS combustion with CaO additives were investigated by an online thermogravimetric-mass spectroscopy-Fourier transform infrared (TG-MS-FTIR) spectroscopy system and a fluidized combustion reactor system, respectively. Results indicated that CaO significantly reduced the emissions of SO2 and NOx during fluidized combustion of OS, and the minerals in OS and CO2 in the flue gas affected the utilization efficiency of CaO additive. The sulfur fixation capacity by CaO decreased with the increase of combustion temperature and almost completely failed at 1100 degrees C. The capacity of CaO to reduce NOx emission increased first followed by a decrease with the increase of combustion temperature. Furthermore, CaO significantly promoted the conversion of HCN to other nitrogen-containing gases, which can promote the production of NO by the precursors (HCN and NH3) and the reduction reaction of NO to N-2. To the best of our knowledge, there is still not an efficient and clean technology for large-scale treatment of OS in China. This study is helpful for the massive utilization of high-sulfur-containing OS.