Bacterial cellulose (BC) nanofibers were biosynthesized by Acetobacter xylinum NUST5.2, and displayed a remarkable capability for orienting TiO(2) nanoparticle arrays. Large quantities of uniform BC nanofibers coated with TiO(2) nanoparticles can be easily prepared by surface hydrolysis with molecular precision, resulting in the formation of uniform and well-defined hybrid nanofiber structures. The mechanism of arraying spherical TiO(2) nanoparticles on BC nanofibers and forming well-defined, narrow mesopores are discussed in this paper. The BC/TiO(2) hybrid nanofibers were used as photocatalyst for methyl orange degradation under UV irradiation, and they showed higher efficiency than that of the commercial photocatalyst P25.