Abstract: The Easy%R_omodel,in which only temperature and time were considered,was calibrated to take into consideration the suppression of vitrinite reflectance by hydrogen-rich organic matter and overpressure.A new model was developed by introducing a hydrogen-rich correction coefficient and overpressure inhibiting coefficient.Using the data collected from both the double-suppressed wells and the normal wells in the West Bozhong Sub-depression of Bohai Bay Basin,China, some relative parameters were determined and the model was tested.The results show that the computed vitrinite reflectance values in double-suppressed formation agree with the mea-sured data,but are significantly different from those predicted by the Easy%R_omodel.And the vitrinite reflectance values were reduced by 0.2%~0.4% in double-suppressed formations. Organic matter maturation was retarded by overpressure.It led to the increase of depths of the hydrocarbon generation threshold and the delay of time of hydrocarbon generation,which was advantageous for late hydrocarbon accumulation.