BiOCl is known as a highly efficient photocatalyst for degradation of pollutants. However, effective methods for fabricating BiOCl nanomaterials with well-defined facets are still lacking. In this work, a facile synthetic method was developed for the fabrication of BiOCl nanodisks with exposed {001} facets. The central feature of this approach was the use of water as the hydrolysis agent and ethylene glycol as the crystal growth inhibitor agent to tune the growth of BiOCl nanomaterial. With this approach, the size and shape of BiOCl nanostructures could be effectively tuned through adjusting the volume ratio of ethylene glycol/H2O. In addition, the mechanism of the crystal growth in this fabrication process was elucidated. The as-prepared BiOCl nanodisks with exposed {001} facets exhibited an excellent photocatalytic activity towards Rhodamine B degradation under both ultraviolet and visible light irradiations. These findings shed light on the deep understanding of formation mechanisms of BiOCl nanodisks and provide an efficient and facile method for the synthesis of high active photocatalyst.