In this work, the photocatalytic degradation of RB5 dye by bismuth oxide nanoparticles (Bi2O3) and loaded with silver metal (Ag@Bi2O3) were investigated. Bismuth oxide nanostructures were prepared by hydrothermal method. To evaluate the morphology, size and morphology of prepared nanoparticles, the different techniques including X-ray diffraction (XRD) technique, ultraviolet-visible (UV-Vis) spectroscopy, field emission scanning electron microscopy (FESEM), X-ray energy diffraction spectroscopy (EDX) were employed. The effect of various factors including pH, amount of photocatalyst, concentration of dye, ultrasound waves and different percentages of Ag doped on RB5 dye degradation was investigated. The results showed that the band gap energy of Ag@Bi2O3 and Bi2O3 are equal to 2.46 and 2.65 eV, respectively. The results of different silver doped percentages showed that 2% had the highest RB5 dye degradation under visible light. Experimental results showed that pH=7 has the best effect on photocatalytic degradation. Comparing photocatalytic and sonophotocatalytic experiments performed for Bi2O3 and Ag@Bi2O3 to degrade RB5 dye, a higher percentage of degradation was observed in the presence of ultrasound waves than in the absence of these waves. The different amounts of Bi2O3 and Ag@Bi2O3 photocatalysts used for degradation; the concentration of 5g L-1 had the greatest effect on the degradation of the pollutant. Photocatalytic degradation of RB5 dye by bismuth oxide nanostructures follows a pseudo-first-order kinetic model. The results also showed that photocatalytic activity of Ag%2@Bi2O3did not decrease after five cycles.