Coal samples from coal-fired power plants and sludge samples from domestic sewage treatment plant were collected in Linhuan Industrial Park in Huaibei, Anhui Province. The co-combustion experiments of coal and sludge under different mixing ratios were carried out by thermogravimetric analysis (TGA). The kinetics analysis of the mainly weightlessness stage of fuel was studied by five reaction kinetics models, and the combustion characteristics of coal and sludge were revealed. Results showed that the coal sample had one weight loss peak at the temperature of 529℃ while sludge had three ones at the temperature of 140, 293 and 430℃, indicated that the combustion process of sludge was divided into three stages of weightlessness while coal only had one stage of weightlessness. The flammability index and combustion characteristics index of coal were 11.36×10–6 mg/(K–2•min) and 47.1610–10 K–3•min–2. Compared with coal, the flammability index and combustion characteristics index of sludge were lower, 10.74×10–6 mg/(K–2•min) and 13.04×10–10 K–3•min–2, respectively. The combustion characteristics of the reaction was increased by adding sludge to coal, and the mixing ratio was preferably 90 (coal): 10 (sludge). As the heating rate increases, the weight loss of coal and sludge decreases, and the burning weight loss rate increases. The DTG curves of all samples were shifted to the high temperature side, resulting in thermal hysteresis. During the fixed carbon burnout phase, the activation energy of the blended fuel was between the two kinds of raw materials, and decreased with the addition of sludge, which proved that the addition of sludge can effectively improve the reactivity of coal and promote its combustion process.