The combustion characteristics and gas emissions behavior of Low-calorie Indonesian coal (LC), Shaanxi coal (SC), and Datong coal (TC) were analyzed by a thermogravimetric-Fourier transform infrared spectrometer (TG-FTIR). The results showed that LC was the easiest coal to burn, followed by SC and TC. The main components of LC ash were alkali metals and alkaline earth metals (AAEMS), while SC and TC were clay minerals. The catalytic activity of LC ash was higher than that of SC and TC ash. FTIR results indicated that the main functional groups of three coals were CO