Abstract: This paper centers on the study of the characteristics of the series of fluorene and C₆ compound in the condensate and the light oil associated with natural gas, and deals with sedimentary environments and the gas-source rocks. After GC and GC-MS methods were applied for analysis of more than 40 samples from basins in China, these singifie ve data suggest as ffollows: (1) There are obvious differences among the contents of C₆ compounds in the condensate and the light oil derived from the different sedimentary en romnents. The series of C₆ composition in the light hydrocarbon related to the lacustrine-fluvial fades is characterized by higher contents of n-hexane and i-hexane, related to the saline lake fades by relativety higher of benzene and related to the marine facies by higher contents of cyclohexane and methylcyclopenta Moreover, consequent upon the different coal-forming environments, the composition of the condensate which from the coal-bearing series is of some differences. (2) The series of fluorene compound in aromatic hydrocarbon is composed of fluorene, oxygen-bearing fluorene and sulfur-bearing fluorene (F. OF and SF for short). The abundances of these three parts present obvious difference due to derived from various parent materials and sedimentary environments. The condensate from the freshwater lacustrine environment is of higher fluorene content, associated with salt lake and marine presents abundant in sulfur- bearing fluorene and related to the coal- bearing series and swamp sedimentary environment abundant in oxygen- bearing fluorene. Therefore, it is proposed that the series of fluorene compounds and other sulfur-bearing aromatic hydrocarbons could not only be used as one of the main indicators of gas-source matter and sedimentary envoronment but also used to identify genetic types of natural gases.