Well-defined cell ulose-based dual graft molecular brushes, composed of ethyl cellulose-graft-poly(N,N-dimethylaminoethyl methacrylate)-graft-poly(epsilon-caprolactone) (EC-g-PDMAEMA-g-PCL), have been prepared by ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP). Unlike other brush copolymers, the new molecular brushes show some unique physicochemical properties and multifunction due to their unique topological structures. These biocompatible copolymers self-assembled to micelles in aqueous solution. Upon pH change, the single micelles further assembled into micellar aggregates. As a result, the micelles in aqueous media could act as excellent drug nanocarriers for controlled drug release. The crystallinity and crystal morphology of the copolymers can be controlled to a certain extent by varying the length of the side chains, which may exert strong spacial restriction and, hence, affect the crystal structures.