Monte Carlo simulation method was used to investigate the self-assembly behavior of two triblockco polymers with different hydrophilic block lengths, i.e., ABA and CBC ,as well as their mixtures ABA/CBC.in selective solvents of A and C blocks. The simulation results indicate that by regulating the hydrophobic interaction between the B block and the solvent , both triblock copolymers can self-assemble to form polymer vesicles with hydrophobic block B as the membrane and hydrophilic block A ( or C ) covering the surface of the hydrophobic membrane. When these two types of tribloek copolymers are mixed together, simulation results show that by adjusting the mixing ratio , asymmetric vesicles with asymmetric membrane structures can beformed with long hydrophilic blocks (C )on the outside and short hydrophilic blocks ( A ) inside. This asymmetric vesiclc has unique application value in the field of biomedieinc ,and our simulation results providencw ideas and necessary theoretical basis for the preparation of asymmetric vesiclcs.