Abstract: The chemistry of macerals at elevated maturity in a series Carboniferous coal source rocks, from Shengli Oil field in eastern China was analyzed using Micro-FT.IR.Resultsshow that fluorescent vitrinite was abundant in aromatic and carbon-oxygen structures while resinite and cutinite are rich in aliphatic structures. The aliphatic chain of the fluorescent vitrinite and resinite was shorter and more branched than that of cutinite and sporinite. The ratio of (CH₂+CH₃)/C=C and CH₂/CH₃ of the fluorescent vitrinite and resinite are decrease with the elevation of maturity, while these two ratios of cutinite and sporinite decrease after increasing with maturity, which indicate that vitrinite and resinite are characterized with early maturity to produce immature oil but cutinite and sporinite had a peak hydrocarbon generation during their thermal evolution.