Objective　To　prepare　paclitaxel-loaded　pH-sensitive　block　copolymer　micelles　and　evaluate　the　in　vitro　anti-cancer　effect.　Methods　A　block　copolymer,　poly(ε-caprolactone)-poly(N,N-diethylamino-ethylmethacrylate)-poly　(ethylene　glycol)(PDC),　was　prepared　by　ATRP　and　click　reactions　and　polymeric　micelles　were　prepared.　The　sizes　and　zeta　potentials　of　micelles　were　determined　under　varied　pH　values.　Paclitaxel　was　encapsulated　n　the　micelles.　The　encapsulation　efficiency　and　loading　efficiency　were　measured.　Drug　release　was　investigated　using　dialysis　method.　Human　breast　cancer　MCF-7　cells　were　used　to　evaluate　the　anti-cancer　effect　of　drug-loaded　micelles　by　MTT　method.　Results　The　sizes　and　zeta　potentials　of　micelles　decreased　with　the　increase　of　pH　values.　The　drug　encapsulation　efficiency　was　92.　0%　and　the　loading　efficiency　was　8.　36%.　Under　neutral　environment,　the　mean　size　was　100.　3　nm,　and　the　zeta　potential　was　close　to　zero.　The　micelles　showed　faster　drug　release,　higher　accumulation　release,　and　better　anti-cancer　effect　in　the　low　pH　(6.　5)media　than　n　the　neutral　media.　Conclusion　The　pH-sensitive　block　copolymer　micelles　have　the　merits　of　pH-sensitive　drug　release　and　high　anti-cancer　effect.　It　is　a　promising　anti-cancer　drug　carrier.