Abstract: Composition and structure characteristics of fine slag (FS) and coarse slag (CS) discharged from Texaco gasifier with Zhundong coal as raw material were analyzed, and their thermochemical conversion properties were analyzed. Proximate and ultimate analyses show that the contents of fixed carbon in coarse slag are 42.31%, indicating that it can be used as raw material to realize its high-added utilization. Analysis with Fourier transform infare spectrometer (FT-IR) suggest that the absorption peak of Si−O in coarse slag and fine slag is stronger, and there is a small amount of aromatic structure in fine slag. Thermal decomposition behaviors in inert atmosphere show that the maximum weight loss rate peak of coarse slag is located around 600 ℃, while that of fine slag is transferred to about 620 ℃. Results of thermal decomposition in oxidization atmosphere show that there are obvious weight loss rate peaks derived from combustion of the fixed carbon in 500−700 ℃. The weight loss profiles of fine slag and coarse slag in inert and oxidization atmosphere were fitted by Coats-Redfern method. The kinetic parameters including pyrolysis/combustion activation energy and correlation coefficient were calculated. The results show that the fitting effect is better as the reaction order selected as 3 at the intense pyrolysis section (560−640 ℃) for coarse slag in inert atmosphere, with correlation coefficient R² of 0.99 and activation energy E of 38.85 kJ/mol. Similarly, in the intense pyrolysis stage (590−650 ℃) of fine slag, the fitting effect is better as the reaction order selected 3, with the correlation coefficient R² of 0.97 and the activation energy E of 79.09 kJ/mol. In oxidization atmosphere, at the intense combustion stage of coarse slag (540−605 ℃) and fine slag (530−605 ℃), the fitting effect is better as n=1 for the both slags, with the activation energy E of 226.46 and 154.73 kJ/mol respectively.