The thermal decomposition mechanism of Shichanggou oil shale was analyzed by thermogravimetry, ultimate analysis and XRD, and the pyrolysis characteristics of oil shale at different heating rates were studied. The results showed that the organic matter was mainly cracked in the temperature range from 300 to 550℃, which produced shale oil and gases. As the heating rate increased from 3 to 15℃/min, the pyrolysis was shifted to higher temperatures. The final decomposition of organic matter increased from 530 to 575℃. The pyrolysis activation energy of organic matter calculated by direct Arrhenius method increased from 243.52 to 257.32 kJ/mol when the heating rate increased from 3 to 15℃/min. The activation energy of organic matter pyrolysis calculated by Friedman method increased from 96.39 to 292.84 kJ/mol when the conversion rate increased from 0.02 to 0.97.