Co-combustion of steam desiccation sludge with coal is a technical measure for large scale sludge disposal,but the effect of steam desiccation sludge co-combustion on unit energy consumption characteristic is unclear. The performance test of co-firing coal and sludge dried by steam was conducted in a 350 MW coal-fired power unit. The effects of steam desiccation sludge on boiler thermal efficiency,steam turbine heat rate,auxiliary power consumption ratio,energy consumption rate were studied. During the test,the treatment amount of raw sludge was set at 8.00 t/h,and the moisture content of the raw sludge was dried from 80% to 60% and 40% respectively by sludge dryer. The results show that the unit energy consumption rate has an increasing trend when the power unit blends with steam desiccation sludge. The decrease of boiler efficiency is mainly due to the increase of sensible heat loss in exhaust flue gas and unburned carbon heat loss in residue. The steam consumption during sludge desiccation leads to the increase of the steam turbine heat rate. The increase of power consumption of fan system and desulfurization system causes the increase of the auxiliary power consumption ratio primarily. The higher the degree of sludge drying is,the smaller the decrease of boiler efficiency is,the greater increasing extend of the steam turbine heat rate is,and the smaller increasing extend of the auxiliary power consumption ratio is. When the sludge moisture content is dried from 80% to 40%,the net fuel consumption rate reduces slightly,whose variation reduces from 2.039 g/kWh to 1.904 g/kWh. As the power unit blends with raw sludge,the decrease of the boiler thermal efficiency and the increase of the auxiliary power consumption ratio are the main factors causing the increase of energy consumption rate. As the power unit blends with steam desiccation sludge,the increase of the steam turbine heat rate is the key factor leading to the increase of energy consumption rate. This study provides the theory and data support for evaluating the energy consumption of the power generation coupled with steam desiccation sludge.