Incineration treatment is the main disposal method of domestic sludge in my country. Mixing combustion with coal is one of the research hotspots, but it is less researched and applied in small-scale coal-fired units. Based on the 210 MW four-corner tangential-circle coal-fired unit of a domestic power plant, field tests of mixing domestic sludge for 8 working conditions were carried out, respectively, and the monitoring data and test results were compared and analyzed. The results show that ash content and the sulfur content increase gradually with the increase of sludge blending ratio, the calorific value of the fuel decreases gradually. For solid products, since the content of heavy metals in sludge is higher than that of coal, the content of heavy metals in fly ash, slag and desulfurized gypsum increase after mixed sludge combustion, and there is a risk of secondary pollution. The emission of conventional flue gas pollutants NOx,SO2 and dust is less affected by the mixed burning of sludge, and the existing flue gas purification process can meet the ultra-low emission requirements of coal-fired flue gas.After mixed burning of sludge, the concentration of heavy metals and their compounds and other pollutants increase by about 3.6 times at most. Under full load condition, when 10% sludge is mixed burning, the average mass concentration of dioxin is 0.021 ng/m3 (calculated by toxic equivalent concentration TEQ), but it still meets the relevant emission requirements. When 10% domestic sludge is mixed, the average temperature in the furnace only decrease by 15 ℃, and the decrease in thermal efficiency is less than 0.5%, the effect is not significant.