Digital　holographic　microscopy　is　a　promising　quantitative　phase-contrast　imaging　technique,　which　exhibits　the　advantages　of　non-destruction,　full　field　of　view,　quasi-real　time,　and　don＇t　need　dye　and　external　marker　to　the　living　biological　sample.　In　this　paper,　the　inverted　off-axis　image-plane　digital　holography　with　pre-magnification　is　built　up　to　study　the　living　MDA-MB-231　breast　cancer　cells.　The　lateral　resolution　of　the　proposed　experimental　setup　is　0.87　mu　m,　which　is　verified　by　the　standard　USAF　test　target.　Then　the　system　is　used　to　visualize　the　interaction　between　living　breast　cancer　cells　and　drug.　The　blebbing　is　observed　after　the　cells　are　treated　by　paclitaxel　drug,　and　the　distribution　of　the　paclitaxel　inside　the　cells　is　detected,　which　is　near　the　cytomembrane,　or　in　other　words　the　end　of　the　microtubules.　It　will　stop　the　mitosis　and　cause　the　death　of　the　cells.　It　is　helpful　to　reveal　the　anticancer　mechanism　of　paclitaxel　in　the　subcellular　scale.