Abstract: The influence on the electrolysis curve of the voltage and current and the aggregation of the liquid magnesium by different addition volume of the electrolysis residue are studied in this paper. The results show that the collect of the liquid magnesium severely affected by the electrolysis residual， and which becomes electric conduction substance due to adsorption magnesium. So the electrolysis system appears those phenomena of the electric conduction， the inequality electrode current and rapidly declining voltages with the electrolysis residual increasing， and which also break the aggregation of the liquid magnesium and produce magnesium particle， and moist angle will decrease due to cathode surface covered by electrolysis residual is the primary cause. Magnesium adsorbed by electrolysis residual is the main reason for declining current efficiency at the residual content below 6%，and the current efficiency reduced by the electronic short circuit between anode and cathode at the residual content over 6%. Refining electrolyte and electrolyzing by protection atmosphere can effectively reduce the residue production.