Reversible addition fragmentation chain transfer (RAFT) dispersion polymerization was utilized to synthesize poly(methacrylic acid)-b-poly(butyl acrylate) (PMAA-b-PBA) amphiphilic block copolymer dispersions in methanol by using the PMAA homopolymer with dithiobenzoate end-group as macro-RAFT agent. And the PMAA macro-RAFT agent was synthesized first by using 4-cyanopentanoic acid dithiobenzoate (CADB) as RAFT agent, where the intermolecular hydrogen bondings can be formed between the MAA units. With the formation of solvophobic PBA block by propagating BA monomer on the PMAA homopolymer chain, the PMAA-b-PBA block copolymer in situ self-assembled into core/shell sphere with PBA and PMAA blocks as core and shell matrix, respectively. The repulsive steric interaction within the PMAA block on shell matrix stabilized the copolymer particles in methanol dispersion, which further resulted in the formation of wrinkly surface pattern on the PMAA-b-PBA copolymer film. During the film formation process, the core/shell copolymer particles were concentrated and then anisotropically aggregated with the evaporation of methanol. The aggregated copolymer particles further assembled into the fibrous structure, so that the film with wrinkly surface pattern was obtained. And the fibrous Width and the amplitude of fluctuant film surface can be controlled by copolymer molecular structure and film casting temperature, which are synergetically governed by both the self-assembly of core/shell copolymer particles and the hydrogen-bonding network within the PMAA blocks.