Amphiphilic A 2(BC) 2 miktoarm star polymers [poly(ϵ-caprolactone)] 2-[poly(2-(diethylamino)ethyl methacrylate)- b- poly(poly(ethylene glycol) methyl ether methacrylate)] 2 [(PCL) 2(PDEA- b-PPEGMA) 2] were developed by a combination of ring opening polymerization (ROP) and continuous activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP). The critical micelle concentration (CMC) values were extremely low (0.0024 to 0.0043 mg/mL), depending on the architecture of the polymers. The self-assembled empty and doxorubicin (DOX)-loaded micelles were spherical in morphologies, and the average sizes were about 63 and 110 nm. The release of DOX at pH 5.0 was much faster than that at pH 6.5 and pH 7.4. Moreover, DOX-loaded micelles could effectively inhibit the growth of cancer cells HepG2 with IC 50 of 2.0 μg/mL. Intracellular uptake demonstrated that DOX was delivered into the cells effectively after the cells were incubated with DOX-loaded micelles. Therefore, the pH-sensitive (PCL) 2(PDEA- b-PPEGMA) 2 micelles could be a prospective candidate as anticancer drug carrier for hydrophobic drugs with sustained release behavior.