Abstract: Polyaniline nanofiber coating possesses antistatic properties, electromagnetic shielding, gas sensing, and etc, thus it is of great significance for improving product performance to construct large-area polyaniline nanofiber interface with controlled morphologies on general plastic surfaces. We report a combined method based on in-situ polymerization and lithography, i.e. constructing large-area polyaniline nanofiber arrays on polyethylene terephthalate surfaces. The results reveal that the obtained polyaniline coating prepared via the in-situ polymerization possess large-area and uniform nanofiber array structures. Compared with the drop-casting method, the micro-patterns of polyaniline nanofiber prepared via in-situ polymerization have superior precision and binding capacity with the substrates. Meanwhile, the polyaniline nanofiber sensors via in-situ polymerization show better humidity sensing performance and superior repeatable stability.