The delta-Bi2O3/Bi2MoO6 composites were synthesized by hydrothermal method and the microstructure and photocatalytic property were characterized. The X-ray diffraction (XRD) analysis revealed that delta-Bi2O3 was obtained with the existence of Bi2MoO6, while the product was alpha-Bi2O3 without Bi2MoO6 under the same experimental condition. The SEM images and the selected area electron diffraction (SAED) patterns have further verified that delta-Bi2O3 was deposited on Bi2MoO6. The X-ray photoelectron spectroscopy (XPS) spectrum confirmed that the composites were composed of delta-Bi2O3 and Bi2MoO6, while a fraction of Mo changed from Mo6+ to Mo5+. The coexistence of Mo5+/Mo6+ can be a critical factor in the formation of stable delta-Bi2O3 on Bi2MoO6 . Particularly, the delta-Bi2O3/Bi2MoO6 photocatalysts possess favorable photocatalytic performance under simulated sunlight illumination since the recombination of photogenerated electrons and holes was inhibited due to the p-n junction at the interface of delta-Bi2O3 and Bi2MoO6, and the mechanism was discussed in detail.