Abstract: To study the influence of blending ratio of paper sludge on operating characteristics of a 130 t/h CFB coal-fired boiler, thermodynamic equilibrium calculation and flue gas/air resistance calculation were carried out. Results show that with the rise of blending ratio of paper sludge, the furnace exit gas temperature drops, the exhaust gas temperature increases, the boiler efficiency reduces, the inlet dry sludge rises significantly, the inlet coal quantity reduces slightly, the flue gas flow, fly ash mass and the attempering water flow increase remarkably, the primary/secondary air resistance and the flue gas resistance increase in rising gradient. Above results may serve as a reference for the retrofit of CFB coal-fired boilers to co-fire sludge.