The kinetic expression commonly used in the thermal analysis of oil shale pyrolysis was derived on the basis of a simple first order kinetic equation of kerogen decomposition. The activation energy, as well as the reaction rate constant of oil shale pyrolysis could be determined by using non-isothermal (NI) or isothermal (I) TG. However, the kinetic parameters determined by using either NI or I did not enable the good prediction of the kerogen conversion at other conditions.