The invention belongs to the technical field of photocatalytic nanomaterials and discloses an Au modified TiO2/WO3 heterojunction nanofiber photocatalyst and a preparation method and application thereof. The preparation method of the photocatalyst includes: 1) adding polyvinylpyrrolidone, ammonium tungstate, butyl titanate and chloroauric acid into an ethanol and acetic acid mixed solution, and well mixing to obtain a precursor solution; 2) taking the precursor solution for electrostatic spinning to obtain nanofibers, and calcining to obtain the photocatalyst. By construction of TiO2/WO3 heterojunction, compounding of photoinduced electron-hole pairs can be effectively inhibited; by addition of precious metal Au for modification, response performance of the photocatalyst to visible light is improved under plasma resonance effect of Au, and accordingly photocatalytic hydrogen output rate is increased. In addition, By a one-dimensional nanostructure of electrospun fibers and a unique fiber mat structure, photocatalyst separation and recovery efficiency is improved, and reusability of the photocatalyst is improved.