Method for removing metal salt in diamine acid gas absorbent

The method for removing the metal salt in the diamine acid gas absorbent comprises the following steps: introducing the diamine acid gas absorbent for absorbing SO2 into a diamine cation protective agent reaction unit, and then adding a cation protective agent, so that the pH value in the diamine cation protective agent reaction unit is maintained at 10.5-12; then pumping a diamine solvent in the diamine cation protective agent reaction unit to an electrodialysis desalination unit for desalination; and the cationic protective agent is sodium or potassium hydroxide with the concentration of 10-50%. The method has the beneficial effects that the diamine cation protective agent is added into the reaction unit, so that diamine is converted from an ionic state to a non-ionic state, and the migration loss of solvent cations of the electrodialysis unit is reduced; a diamine solvent completely reacted with a protective agent is pumped to an improved electrodialysis desalination unit, metal salt in the solvent is remo