A new approach to self-assembly of polymer blends in solution was studied by dynamic light scattering and transmission electron microscopy. Stable isolated particles and their clusters were obtained by dropping sulfonated polystyrene/THF solution into poly(4-vinyl pyridine)/methanol solution. The particles and clusters are stabilized by soluble poly(4-vinyl pyridine). The concentration of poly(4-vinyl pyridine) in methanol prays an important role in the self-assembly of polymer blends. Only in a suitable concentration range, stable particles can be prepared. Gelation appears at high poly(4-vinyl pyridine) concentration, while precipitation of sulfonated polystyrene occurs at low poly(4-vinyl pyridine) concentration.