Perovskite-type alkaline niobate nanofibers were prepared by electrospinning. KNbO3 nanofibers with lower BET exhibit higher photocatalytic efficiency than NaNbO3 with similar phase structure and morphology. The internal electric field, which does not exist in antiferroelectric NaNbO3, induced by spontaneous polarization in ferroelectric KNbO3 can promote the separation and accelerate the movement of photogenerated charge carriers.