According　to　the　mixing　principle　of　vortex-generated　enhancing,　a　passive　micromixer　arranged　with　the　vortex-generated　structures　was　proposed.　Three-dimensional　numerical　simulation　was　carried　out　with　adoption　of　Computational　Fluid　Dynamic　software　in　this　paper.　The　finite　volume　method　was　used　to　disperse　the　three-dimensional　steady　incompressible　N-S　equations.　Mixing　index　is　measure　standard　used　to　evaluate　the　degree　of　mixing.　The　effect　of　mixing　performance　was　analyzed　when　changing　the　volume　flow　from　0.18　μL/min　to　1.75　mL/min　of　this　micromixer.　Our　studies　show　that　the　structural　parameters,　e.g.　different　aspect　ratio　of　microchannels　and　the　inflow　angle　of　separation　channel,　have　an　important　effect　on　the　mixing　performance.　Taking　account　for　the　relation　between　mixing　intensity　and　structural　parameters,　when　symmetrically　arranged　two　double　gaps　structures　with　an　angle　of　minus　45　degrees,　this　passive　micromixer　could　achieve　the　optimum　mixing　performance.