Abstract: The CO₂ gasification reactivity of coal chars blended with different proportions of coarse slag were investigated by using an STA449F3 thermo-balance in the isothermal mode at the temperature range from 900 ℃ to 1 380 ℃. The thermal behavior of the sample was studied using thermo-gravimetric analysis and differential scanning calorimetry (TG-DSC), and the two regions (i.e. the low temperature region and the high temperature region) for the gasification reactivity and carbon conversion of coal chars were defined according to the flow temperature of coal ash fusion. The gasification reactivity and carbon conversion of coal chars with coarse slag added are improved in the low temperature region. But the addition of coarse slag decreases the carbon conversion, and the gasification reactivity of coal chars blended with coarse slag to certain ratio also decreases in the high temperature region. It is indicated that the initial gasification reaction of coal chars is chemically controlled in the low temperature region, and diffusively controlled in the high temperature region.