Design and controllable synthesis of photocatalysts and tailoring their catalytic property such as degradation performance of organic dyes are an interesting subject. We reported the preparation of nitrogen-doped carbon quantum dots/TiO2 composites (N-CDs/TiO2) by hydrothermal process using urea and tetrabutyl titanate (TBT) as precursors. The morphology and chemical structure of N-CDs/TiO2 (N-CDs/TiO2-X, where X is the mass ratio of urea to TBT) were characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and electron paramagnetic resonance. We found that the fine N-CDs have the specific properties that it can tune the growth behavior of TiO2 in micrometer size. With the decrease in the ratio of N-CDs to TBT, the morphology of as-fabricated N-CDs/TiO2 changes from hollow spheres, honeycomb to agglomerations bulks, with changing their crystalline phase accordingly. The degradation testing of rhodamine B (RhB) under visible-light irradiation (lambda >= 400 nm) shows that the photocatalytic performance of N-CDs/TiO2-X substantially improved relative to pure TiO2, while calcinations process substantially decreased the catalytic activity. The optimal photocatalytic performance of N-CDs/TiO2(-)1 totally removed the RhB in 120 min, which is 11.42 times over that of TiO2. Radical trapping experiment and EPR spin-trapping study show that the center dot O2- radical and h(+) were the main active species that account for the photodegradation performance.