In this work, we present a new concept of aquous flow battery deionization (FBDI) system based on dual-ions electrochemistry, which consists of BiOCl as chloride-capture anode, sodium manganese oxide (Na_0.44MnO₂) as sodium-capture cathode. It utilizes a redox reaction to individually absorb chloride ion at anode and sodium ion at cathode at the same time. When charged, the two ions are released to flow sodium chloride electrolyte solution. Upon discharge, the chloride ion was extracted into the anode from flow NaCl solution while sodium ion was electrochemically captured into the cathode. The novel battery deionization delivers a stable and reversible salt absorption/desorption capacity of 68.5 mg g^-1 with ~100% columbic efficiency when operated at a current density 100 mA g^-1, which makes over twice salt absorption of the previous reported best performance (31.2 mg g^-1) obtained by a hybrid capacitive deionization system. The “ion/electron transfer efficiency” as a new concept was proposed to replace the “charge efficiency”, since the salt was removed during the discharge process, which is the first time to report thus a phenomenon. The ion/electron transfer efficiency is up to 0.977 during charge-desorption process and 0.958 during discharge-absorption process. Owing to salt removal during discharge, the current system is called “desalination generator”. The current study will supply a new view of desalination and flow battery system.