This paper mainly studied the weight loss of original organic matter, carbon, hydrogen and nitrogen of I, Ⅱ and Ⅲtypes kerogen by means of the chemical reaction kinetics, and the kinetics parameters of weight loss of kerogen and their organic carbon, hydrogen and nitrogen of Ⅰ, Ⅱ and Ⅲtypes kerogen are determined and calibrated by opensystem thermal simulating experiment. These kinetics parameters obtained can be used to calculate the amount of original organic matter, organic carbon, hydrogen and nitrogen in source rocks. Using the special kinetic software, the kinetic parameters then are applied to calculate the recovery coefficients of organic carbon abundance and atomic H/C and N/C ratios. The result shows that when Ro being between 0.47% and 3.05%, the coefficients of the recovery of the original organic carbon abundance, carbon, hydrogen and nitrogen, atomic H/C and N/C ratios for type I kerogen are from 1 to 1.89, from 1 to 1.96 , from 1 to 2.13, from 1 to 0.56, while the coefficients of the recovery for type Ⅱ kerogen are from 0.98 to 1.05 , from 1 to 1.06 , from 1 to 1.89, from 1 to 0.66 and for type Ⅲ kerogen are from 1 to 0.82, from 1 to 0.83, from 1 to 1.59, from 1 to 0.56, respectively. Thus, the abundance of residual organic carbon must be recovered when the potential of hydrocarbon generation are estimated for type Ⅰ and Ⅲ highmature and overmature kerogen, while the abundance of residual organic carbon need not be recovered for type Ⅱ kerogen. Atomic H/C ratios all need be recovered for all types of kerogen. In this paper, the recovery kinetics established for kerogen type Ⅰ, Ⅱ and Ⅲ may be used to calculate the residual organic matter or organic carbon during thermal evolution in an open system.