In this work, the influences of sewage sludge conductivity on the electro-dewatering (EOD) effect and energy consumption under constant voltage were evaluated. The results showed that on adding NaCl solution to the sludge, the average water content in 20min decreased with the increasing electric current. However, the energy consumption increased with increasing conductivity. Decreasing the sludge conductivity by deionized water washing had little impact on the average water content. However, the energy consumption decreased with the reduction of electric current. To sum up, increasing the conductivity can help shorten the EOD time, but decreasing the conductivity can lower the energy consumption of EOD.