Ion chromatography and flame atomic absorption were used to analysis condensates collected in various temperature and slag. The results show that the main components of slag were FeCl2/FeCl3、NiCl2、CrCl2/CrCl3; the condensates were made up of CaCl2、HCl、HClO、H2O and metal chlorides. So the gas in reactor included Cl2、HCl、HClO、H2O、Ar and metal chlorides. The 1.0 L/min argon flow in reactor at 850 °C was simlated to find that it was very difficult to vent the HCl、HClO, et al., so these gases were reacted with reactor wall to produced metal chlorides, which led to seriously corroded, at the same time, HCl、HClO could impact in electrodeoxidation. Based on simlation and tail gas absorption experiment, argon flow increased to 5.0 L/min in 2 h of pre-electrolysis could effectively vent the HCl、HClO, et al. This improvement could enhance the electrolysis velocity and resolve the corrosion problem.