Abstract: Nature of twenty kerogen samples from Daqing Oilfields different in type and degree of maturity were investigated using solid state C-13 nuclear magnetic resonance spectroscopy with cross polarization (CP) and magic angle spinning (MAS) techniques. Carbon-13 chemical shift data of seven kerogen structure related model compounds provide knowledge about general patterns of aliphatic and aromatic bands in a C-13 NMR spectrum of kerogen. For the aliphatic band, peak height of the band will be centered around 30 ppm owing to the high abundence of long chain methylene carbons, while methyl, methine, cyclic methylene and oxygen bonded carbons broaden the band width at the half-height. For the aromatic band, the chemical shifts of protonated and bridged carbons concentrate in the range of 125-130 ppm, but will be scattered to 100-160 ppm due to the contribution of alkyl and oxygen substituted aromatic carbons. The apparent carbon aromaticity(f_a), ratio of peak height to width at half height of aliphatic and aromatic bands(h₁/B₁ and h₂/B₂) derived from NMR spectra represent the chemical structure of kerogen, and are found having good linear relationships with H/C. These parameters may be used for classifying the kerogen types and measuring the degree of maturity. An immature type I kerogen has a low carbon aromaticity f_a, say less than 0.23, high h₁/B₁, ranged 16～32 and low h₂/B₂ ranged 1-2; while for a type Ⅲ kerogen, f_a will be higher than 0.5, h₁/B₁ lower than 6 and h₂/B₂ ranged 7～16; the intermediate values are assigned to the type Ⅱ kerogen. A diagram plotted with h₁/B₁ and h₂/B₂ is suggested to illu-strate the kerogen evolution path of different types.