Abstract: Samples from K1a coal seam in the Zhongliangshan mine were investigated by microscopy and organic geo- chemistry. The coal facies parameters show that the Zhongliangshan coal formed in wet forest swamp under reductive environment,and the coal-forming plants were mainly woody plants. After Soxhlet extraction and group components separation,the composition and molecular geochemical features of organic matter were analyzed by gas chromatograph (GC) and gas chromatograph-mass spectrometry ( GC-MS). The results indicate that the coal-forming plants were mainly terrestrial higher plants. However,the input of marine phytoplankton cannot be excluded. The coal-forming en- vironment was reductive,and the coal seam underwent relatively higher thermal evolution. Aromatic hydrocarbons were dominated by naphthalenes,phenanthrenes and biphenyls. The isomers of aromatic hydrocarbons with higher thermody- namic stability had an advantage position,and the contents of dibenzothiophenes were higher than dibenzofurans,which also implies the reductive coal-forming environment. The results from microscopic and the organic geochemical analy- ses verify mutually.