Abstract: Based on thermal simulation and various analytical experiments, the authors have made a deep research on the structure of kerogen, which shows. 1. the oxygen-enriched type of kerogen possesses inner catalytical effect which exceeds that of clay minerals. 2. aging and alteration of the primary structure of kerogen took place during geological history, many heteroatomic chains of kerogen broke down, and the rate of thermal degradation was reduced. This study provides theoretical evidence for studying mechanism of thermal degradation of Kerogen.