Self-assembled nanostructures of amphiphilic block copolymers hold great promise for applications in nanomedicine. Blending polymers provides all effective way to produce multi functional drug delivery vesicles at micro- and nanoscales. Here we investigate the self-assembly of homopolymer and diblock copolymer blends in a selective solvent by using the self-consistent field method. It is fund that self-assembled nanostructures of different sizes and shapes (e.g., vesicles, circle- and line-like micelles, and their mixtures) can be obtained by varying the concentration and composition of the diblock copolymer. As the chain length or concentration of the homopolymer changes, morphological transitions may occur among the different nanostructures. Oil the basis of a number of simulations under various conditions, a phase diagram of aggregate morphologies is Constructed with respect to the mixture ratio and the homopolymer chain length. The theoretical method presented here Could be used to design novel nanomedicine carriers and to optimize their sizes and shapes for specific biomedical applications.