3D BiOCl hierarchical nanostructures assembled with nanosheets have been successfully synthesized via a facile solvothermal route with Bi(NO3)(3), KCl, poly(vinylpyrrolidone) (PVP), and diethylene glycol (DEG). Photocatalytic experiment illustrated that the as-synthesized BiOCl nanoflowers exhibited superior photocatalytic activity than that of BiOCl microrods and Degussa P25 in the degradation of single and mixed dye solutions under UV irradiation, which has not been reported previously. Besides, the stability of the product in mixed organic dye photodegradation process was also investigated for the first time.