With　aging　population　and　people＇s　demands　to　improve　their　quality　of　life,　stress　urinary　incontinence　(SUI)　patients　who　need　to　be　cured　are　increasing.　Mechanics　plays　an　important　role　in　the　formation　of　SUI.　Muscles　and　other　soft　tissue　in　pelvic　cavity,　which　is　the　direct　control　of　the　mechanical　mechanism　of　urethral　closure,　will　be　important　scientific　issues　in　the　field.　Establishing　mathematical　model　of　bladder-urethra　system　can　provide　a　basic　analysis　for　the　disabled　urethra　closure　of　SUI　in　clinic.　With　the　help　of　computational　fluid　dynamic　(CFD),　we　developed　a　three-dimensional　urodynamic　bladder-urethra　system,　which　includes　bladder,　bladder　neck,　prostate　and　urethra,　and　the　realistic　recirculation　process　of　the　urinary　bladder　during　the　physiological　voiding　process　in　conjunction　with　a　flow　simulation　through　the　female　urinary　bladder　and　urethra　is　presented.　The　computational　results　show　that　a　dead-water　zone　and　a　zone　of　secondary　flow　occur,　and　that　is　independent　of　the　shape　of　the　prostatic　urethra.　For　the　pathological　prostata,　the　extreme　constriction　of　the　prostatic　urethra　results　in　an　additional　wide-stretched　dead-water　zone.　The　simulation　results　not　only　can　improve　urinary　incontinence　surgery　for　clinicians,　but　also　can　provide　a　basis　for　theoretical　analysis.　©　2010　International　Federation　for　Medical　and　Biological　Engineering.