The bio-inspired hierarchical structure of polyaniline (PANI) was fabricated in the pore surface of polymer film through interfacial polymerization. The porous polystyrene (PS) honey-comb patterned (HCP) film containing benzoyl peroxide (BPO) was first fabricated by the breath figure (BF) method under humid conditions, further, the film was immersed into aniline hydrochloride aqueous solution for the interfacial polymerization of PANI. The interfacial polymerization of the HCP porous film led to the biomimetic growth of PANI in fractal configuration for a bio-inspired snowflake or leaf-like pattern in the pore surface. The bio-inspired structure of PANI in the HCP porous film through interfacial polymerization is explained by the diffusion-leading aggregation (DLA) by the reaction of aniline monomer into an aqueous solution and self-assembled BPO in the pore surface. The morphology of the bio-inspired PANI structure in the HCP film was highly sensitive to pH, and revealed the conductivity variation over several orders of magnitude (10-3 to 10-1 S/cm) similar to a smart material. Due to the high pH sensitivity, the film can be applied in various biomedical sensing applications.