Loading filler onto the polymer particle with specific morphology is an effective way to construct filler networks. Here, non-solvent-induced phase separation and vacuum-assisted filtration are used to prepare polymer particles and Al2O3@Polymer composite films. The content and variation of Al2O3 loading are obtained by thermogravimetric analysis after ultrasonication treatment to films, showing that dendritic particles can be stably loaded with considerable filler compared to lamellae and tiny particles owing to the large specific surface area and "wrapped" structure. On the other hand, adding a good solvent during the blending process enhances the filler loading and network constructing capabilities by softening and changing the particle morphology. However, the excessive good solvent decreases filler loading due to the vanishment of microstructure, meaning a balance between dissolution and softening. Finally, Al2O3@PVA/epoxy composites based on dendritic particles are prepared whose thermal conductivity can reach 0.37 W/(m·K) (37.76 wt% Al2O3), 1.7 times higher than pure epoxy.