Converter blown limestone powder steelmaking process has the advantages of energy saving and high efficiency to meet the needs of low carbon metallurgy. Based on a thermogravimetric-differential thermal analyzer, the effect of high CO2 partial pressure on the pyrolysis behavior of limestone at steelmaking temperatures was investigated at 20 °C/min, 30 °C/min, and 40 °C/min, the kinetic parameters of limestone pyrolysis were calculated by the improved double extrapolation method.