The self-assembly of amphiphilic molecules in a selective solvent and the disassembly of a hierarchical nanostructure are of fundamental interest for investigating biological systems and designing complex nanostructures. These two processes are usually separated from each other. Herein, we demonstrated a unique assembly-disassembly process, sequentially presented in the solvent exchange of polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) using tartaric acid aqueous solution as the nonsolvent. Ellipsoidal particles composed of stacked discs were formed in the early stage; then, they transformed to dissociated discs with the increasing amount of the nonsolvent, presenting a rarely observed combination of selfassembly and disassembly in one process of solvent exchange. The bifunctional tartaric acid interacts with the pyridine of PS-b-P2VP via hydrogen bonding, which may result in the formation of an ellipsoidal suprastructure of stacked discoid micelles in the beginning, whereas the increasing swelling of P2VP in acidic solution and the solvation of tartaric acid in water with the solvent displacement may induce the disassembly of these 3D ellipsoids later. This study deepens our fundamental knowledge of the self-assembly of amphiphilic block copolymers confined in a microdroplet. Besides, the obtained block copolymer nanodiscs possess the chirality of tartaric acid, which may provide the potential in further chiral recognition and chiral separation.