The　quasineutral　limit　and　the　mixed　layer　problem　of　the　bipolar　drift-diffusion　model　for　semiconductors　with　different　mobilities　are　studied　in　one　dimensional　space　in　this　paper.　For　the　general　smooth　doping　profile,　the　general　initial　data　and　the　different　mobilities　of　electrons　and　holes,　the　quasineutral　limit　is　proven　by　the　matched　asymptotic　expansion　method　of　singular　perturbation　problem　and　the　energy　method.