The decrease of the elastic modulus of oil shale during pyrolysis was mainly caused by pyrolysis of kerogen and the deterioration of the oil shale skeleton at high temperature. Combining the thermal curve of oil shale and the change mechanism of the elastic modulus of oil shale, a quantitative model of the elastic modulus of oil shale during pyrolysis was established. The simulation results were in good agreement with the experimental data and showed that with increasing temperature, the rate and extent of decay of the elastic modulus of oil shale were gradually increased. The attenuation ratios of elastic modulus at 500 degrees C, 400 degrees C and 300 degrees C were approximately 68.04%, 56.42% and 48.66%, respectively.