Fulvic acid extracted from weathered coal (Gong Xian) was fractionated on the base of molecular weight differences by means of fractional solution in ethanol-ethyl acetate solvent system. The chemical and spectroscopic data, for various fractions indicate great similarities in gross structures and functional groups. Positive correlation between molecular weight and C, H atomic ratio as well as E₄/E₆ indicates that as the molecular weight of the fulvic acid fractions increases the molecular complexity or aromaticity also increases. Compared with fulvic aoids and humio acids from soil and lake sediment, the fulvic acid extracted from weathered coal has higher free radical contents. By correlating with the structure of fulvic aoid the assignment of some infrared absorption bands is critically reviewed and discussed.