The desulfurization efficiency and mechanism of the calcination of petroleum coke in ammonia atmosphere at lower than 1000 ℃ were investigated through a series of conditional experiments and comparison with other gases such as H_2. The topics of efficiency and reaction mechanism are usually discussed through investigation by means of the Fourier transform infrared spectroscopy(FT-IR), the Brunauer-Emmett-Teller(BET) technique, and the thermogravimetry coupled with the mass spectrometry(TG-MS). Results showed that in addition to H_2, ammonia not only could retain a high desulfurization rate but could also reduce coke loss during the desulfurization process of petroleum coke. The best desulfurization conditions covered a petroleum coke particle size of less than 0.1 mm, a calcination temperature of 800 ℃ in ammonia atmosphere with a flow rate of 10 L/h, and a heating duration of more than 120 min. Ammonia decomposition, H_2 generation, decline in the activation energy of the carbon–sulfur bonds, and petroleum coke with a largest specific surface area at 800 ℃ are the key goals of desulfurization studied thereby. As proved by TG-MS analysis, given a large quantity of H_2, ammonia can be decomposed at the same temperature to completely come into contact with the sulfur species in petroleum coke to generate H_2S. The desulfurization efficiency and mechanism of the calcination of petroleum coke in ammonia atmosphere at lower than 1000 ° C were investigated through a series of conditional experiments and comparison with other gases such as H_2. The topics of efficiency and reaction mechanism are usually discussed through investigation by means of the Fourier transform infrared spectroscopy (FT-IR), the Brunauer-Emmett-Teller (BET) technique, and the thermogravimetry coupled with the mass spectrometry (TG- a high desulfurization rate but could also reduce coke loss during the desulfurization process of petroleum coke. The best desulfurization conditions covered a petroleum coke particle size of less than 0.1 mm, a calcination temperature of 800 ° C in ammonia atmosphere with a flow rate of 10 L / h, and a heating duration of more than 120 min. Ammonia decomposition, H_2 generation, decline in the activation energy of the carbon As evidence by TG-MS analysis, given a large quantity of H_2, ammonia can be decomposed at the same temperature to completely come into contact with the sulfur species in petroleum coke to generate H_2S.