Nitrogen functionalities of volatile of three different rank coals, namely TONGCHUAN lean coal, SHENMO bituminite and YIBIN anthracite, were studied by using Fourier transform infrared spectroscopy (FTIR) equipped with 16 m long path distance gas cell. The detection problem of low content of nitrogen in volatile was successfully solved because of the application of the long path distance gas cell. In the long path distance gas cell, the infrared penetrates the sample more times than in a normal gas cell. Results from the analysis of spectra obtained by FTIR show that there are four functionalities of nitrogen in volatile, including pyrrole-type nitrogen, pyrindine-type nitrogen, pyridine-N-oxide nitrogen, and nitrile nitrogen. Comparison of research results of nitrogen group between coal and volatile suggests that the difference in fate of nitrogen between volatile and coal results from the macromolecular nitrogen group of coal decomposition under the effect of temperature.