The　authors　study　the　electro-diffusion　model　arising　in　electrohydrodynamics　which　is　a　coupled　Poisson-Nernst-Planck　and　Navier-Stokes　system.　On　the　basis　of　the　general　data,　a　more　accurate　approximate　solution　involving　the　effect　of　initial　layer　is　constructed　and　the　quasi-neutral　limit　is　performed　rigorously　by　using　multiple　scaling　asymptotic　analysis.　Hardy-Littlewood＇s　inequality　is　used　to　deal　with　the　singular　terms　caused　by　the　initial　layer　function.