At room temperature, diblock copolymers of PLA-b-PNIPAM and PEG-b-PLA self-assembled into complex micelles with a PLA core and a mixed PEG/PNIPAM shell. By increasing the temperature, these complex micelles could be converted into a core-shell-corona structure composed of a PLA core, a collapsed PNIPAM shell and a soluble PEG corona, and the PEG chains stretched from the inner core to outside, leading to the formation of PEG channels. The PEG channels could be used for the exchange of substance between the core and the external environment. Compared with core-shell micelles, complex micelles with a core-shell-corona structure could avoid the burst diffusion in the release of ibuprofen and inhibit the degradation of PLA by lipase to a certain extent.