Photocatalysis has been extensively studied and developed. To overcome the visible-light irresponsive hindrance, developing novel materials has become a significant promise. Bismuth-based semiconductors were promising candidates with suitable band gaps, and various bismuth-based semiconductors can be prepared via facile methods. Herein, we report a modified hydrothermal method assisted by adding acetic acid in the precursor to prepare Bi2MoO6 with enhanced photocatalytic activity in the degradation of RhB under visible light irradiation. This work provides a new approach to improve photocatalytic activity via adding chemicals in the precursors during the preparation.