We employed a facile method to realize sulfur nanoparticles in situ growth on TiO₂ mesoporous single crystals (MSCs). The prepared photocatalysts were characterized by XRD, Raman, UV-vis absorption spectra, XPS, TEM, FESEM, TG/DTA and photoluminescence (PL) emission spectra. The average sulfur particle size is around 8 nm, and we utilized various volumes of ammonium polysulfide ((NH₄)₂S_x) to tailor the loading of sulfur nanoparticles. When the loading content is 27.2 wt%, they exhibit the optimal photoactivity in degrading acid orange 7 (AO7). In comparison with the pure MSCs (P-TiO₂ MSCs), the removal rate of 30S-TiO₂ MSCs can be enhanced about 90% under solar light irradiation, and after 5 cycles it retains a high photocatalytic performance.