The design and synthesis of novel linear-dendritic diblock amphiphiles with linear poly(acrylic acid) (PAA) as the hydrophilic block and dendritic poly(benzyl ether) as the hydrophobic block are described. The synthetic process consisted of two steps: a poly(methyl acrylate) (PMA)-poly(benzyl ether) dendrimer series were synthesized with atom transfer radical polymerization, and through the hydrolysis of linear PMA. block into PAA, amphiphilic block copolymers, the PAA-poly(benzyl ether) dendrimer series, were obtained. The copolymers were characterized by H-1 NMR, Fourier transform infrared, and size exclusion chromatography and exhibited well-defined architectures and low polydispersities. When the generation number of the dendritic block (G(i)) less or equal to 3 and the degree of polymerization of the linear chain (n) was greater than 10, the amphiphiles were water-soluble. The solution intrinsic viscosity increased with both the length of linear chain and the generation number of the dendritic block. The results obtained demonstrate that dendritic blocks play an unusual role in aqueous solutions of amphiphiles.