A steady-state numerical model for multi-ion parallel-plate electrode (PPE) system is developed to investigate the concentration and electric distribution in the process of salt water electrolysis under forced convection. The finite-element method is used to solve this multi-ion transport model coupled with ionic diffusion, convection and ionic migration. The flow field and the electrode cur-rent's effect on the concentration distribution are investigated. The comparison between the diffusion-transported current and the migration-transported current demonstrates that the current is almost fully transported by the ionic migration, with the result that the diffusion-transported cur-rent can be neglected and the control equation of potential is simplified. For comparison, a hypothetical model with uncoupled situation of concentration and electric field is taken into consideration. The variation of electric field strength near the cathode can reach 25% of the value of the uncoupled model in the condition of u(0) = 0.01 m/s. Compared with this, the variation of ionic electro-conductivity shows a reverse tendency. (c) 2007 Elsevier Ltd. All rights reserved.