Through the selection of N-type organic semiconductor molecules and the method of supramolecular self-assembly at the solvent phase interface, the perylene tetracarboxylic diimide (PTCDIs) nanofiber film with loose and porous morphology was constructed by in-situ deposition on the surface of ITO conductive glass. Then the P-type organic semiconducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) was grown in the fiber interweaving network of this film via quantitative electrochemical polymerization, thus preparing PTCDIs@PEDOT composite film with N-P heterojunction architecture. PTCDIs@PEDOT film has good moisture resistance and improved sensitivity and signal response for gas phase H₂O₂ detection.