The dynamic process of polymerization-induced self-assembly (PISA) is simulated by the dissipative particle dynamics method coupled with the stochastic reaction model. Meaningful comparisons between simulation and experimental results are made. Typical microscopic self-assembly structures are analyzed, and possible dynamic pathways of their formation are proposed. We find that increasing the length of the hydrophobic block leads to the decrease of the size of the vesicle chamber, which further yields the coexistence of vesicles and compound micelles. Moreover, PISA with fast polymerization is proved to experience a different pathway of transition, in which the hydrophobic and hydrophilic blocks undergo a typical flip-flop process to form the final vesicle structure. The simulation study can act as a theoretical guide to achieve the better design or fine regulation of new PISA systems and relevant functional materials.