Using a molecular theory for dilute PEO-b-PNIPAm solutions, we first take the formation of hydrogenbonds between copolymer monomers and water molecules into account, which enables us to studythe impact of temperature on PEO-b-PNIPAm self-assembly effectively by quantitatively describingthe different change of water affinities of two blocks.With the increase of temperature, hydrogenbonds between PNIPAm and water break down dramatically,resulting in the hydrophobic characterof PNIPAm while PEO remains hydrophilic.Amphiphilic copolymers in the aqueous surrounding canaggregate into various structures: micelle and vesicle.According to the equilibrium criterion of theexcess grand potential under the condition of the grand canonical ensemble, we find both structuresare stable and can coexist.Theoretically calculated potentials of mean force of aggregates furtherverify the coexistence of micelle and vesicle, although the low critical solution temperatures of different aggregates are different under this circumstance.Phase diagram as functions of temperatureand the weight fraction of PEO is obtained, which shows different regions of micelle, vesicleand their coexistence.It implies the appearance of two types of micelle-vesicle transition: spontaneous and temperature-induced.