A series of triblock-graft copolymers PEG-b-[PCL-g-P(MEO2MA-co-OEGMA)]-b-PEG were synthesized by combination of ring-opening polymerization (ROP) and atomic transfer radical polymerization (ATRP). The phase transitions induced by temperature have been studied. The synthesized triblock-graft compolymer not only exhibited a hydrophilic, but also have temperature sensitivity. The triblock-graft copolymers could change from random coil to compact globule, yielding a more compact core-shell structure as the temperature was promoted above their LCST. The triblock-graft copolymers solutions appear a gel phase when the copolymers solution has a higher concentration about 30 wt % at room temperature.