Abstract: The flash pyrolysis of three low rank coals in a nitrogen plasma jet at atmospheric pressure has been studied. The results show that coal undergoes very fast reactions with highly reactive plasma species, which produces a large amount of gas and char. The main components of the gas products are hydrogen, methane, carbon monoxide, acetylene and cyanoacetylene. The concentration of cyanoacety-lene in the gas is related to that of acetylene. It is believed that acetylene acts as the precursor of cyanoacetylene. The acetylene yield depends on the coal type and the experimental conditions, and increases as the volatile matter content of coal increases and as the coal feeding rate is reduced. A maximum acetylene yield of 22. 31% by weight on a carbon basis is obtained from Zhalainuoer lignite when the coal particle size is less than 74μm and the coal feed rate is 5.1 g·min-1. The FT-IR spectra reveal that all of the functional groups in coal except some aromatic C-C bonds have vanished during the pyrolysis, and some nitrogen - containing functional groups such as-CN groups are simultaneously introduced into the chars.