Abstract: To investigate the dissolution behavior and its mechanism of small organic molecular compounds from coals with different ranks such as brown coal,long flame coal,fat coal,meager coal and anthracite,the coal samples were ex-tracted in time intervals with tetrahydrofuran( THF). By means of column chromatography and gas chromatography-mass spectrometry (GC-MS),the difference and origin of the extraction rate,group composition and chemical composi-tion of the extracts were analyzed. The results show that the extraction process of the coal samples can be divided into two stages,and the extraction rate is much higher in stage I than that in stage II. Compared with stage I,the extracts in stage II have more hydrocarbons and less non-hydrocarbons. With the increase of extraction time,the types of extracted compounds from different rank coals gradually decreased except brown coal. In the extracts,heterocyclic compounds are abundant in content and more in type. By contrast,the aromatics in the extracts of medium-rank bituminous coal and long-chain alkanes in the extract of low-medium rank coals are more abundant.