A kerogen pyrolysis model based on chemical structure using modified chemical percolation devolatilization (CPD) is proposed and aims to predict product distribution of kerogen and oil shale pyrolysis. Five representative structural units including aliphatic bridge, aromatic cluster, aromatic ether, alkyl and oxygen-containing bridge are selected to build kerogen network model according to its structural characteristics. Kerogen pyrolysis involves in four processes including initial cracking, aliphatic chain reaction, aromatization and condensation expressed by eight chain reactions. Specific volatile products are attributed to various fragments from kerogen network and classified into seven types on the basis of structural features, which allows model to provide product composition. Oil shale is simplified as a linear combination of kerogen and minerals. Model predictions for kerogen and oil shale are compared with experiment data in fixed bed and thermogravimetry analysis. In conclusion, model reflects kerogen pyrolysis based on its structural characteristics and provides reasonable prediction on product distribution.