Sensor　placement　is　one　of　the　key　techniques　for　Health　monitoring　systems.　Based　on　the　effective　independence　algorithm,　an　improved　effective　independence　is　proposed,　which　takes　each　location＇s　frequency　response　function　as　a　weighting　factor　to　update　the　effective　independence　method,　and　adopts　different　frequency　response　functions　for　corresponding　sensors,　such　as　displacement,　velocity　and　acceleration.　The　new　method　concentrates　sensor　positions　in　high　energy　content　regions,　remedies　defect　of　traditional　effective　independence.　Then　applying　the　promoted　EI　method,　three　dimensions　sensor　placement　for　an　extradosed　cable-stayed　bridge　is　studied,　and　two　criterions,　modal　assurance　criterion　and　ability　to　withstand　noise　pollution　criterion　are　employed.　The　results　show　that　the　promoted　EI　method　can　provide　an　effective,　economical　method　for　optimal　sensor　placement.