Abstract: To improve the combustion characteristics and the utilization of high ash slime, the combustion characteristics of the coal sludge and its blended coal were studied by means of isothermal thermogravimetry and kinetic analysis method. A further study was carried out to explore the law of effect of blended coal, lean coal, ratio and temperature on the combustion characteristics. The results show that the inhibitory effect of ash is obvious in the later stage of burning, and the combustion rate becomes slower. The activation energy of coal sludge combustion is 46.92 kJ/mol, which is higher than that of lean coal while lower than that of bituminous coal, thus it is difficult to burn out. The activation energy of sludge combustion can be effectively reduced by mixing HDJZ bituminous coal, but when the bituminous coal is 75%, it can cause "wind scramble". During the initial volatile combustion, a lot of oxygen will be consumed, leading to an insufficient combustion at the stage of char combustion. Obviously, this is unfavorable for the burnout of blended coal. When the HD bituminous coal is 25%, the activation energy of blended combustion is the lowest, and the combustion is stable. By contrast, the mixing of lean coal with coal sludge has little influence on the combustion characteristics, and the characteristic can be aggravated by adding excessive lean coal. From 800 ℃ to 1 200 ℃, as temperature increases, the burnout time decreases and the combustion rate increases, indicating that by increasing temperature, the combustion behaviors can be promoted.