A series of YBO3 samples were obtained by hydrothermal method. The microstructures, morphologies and optical properties of the samples were characterized by XRD, SEM, TEM, XPS and UV-Vis. The photocurrent and electrochemical impedance experimental were researched with CHI660E electro-chemical system and the photocatalytic activities of the samples were tested with the photocatalytic degradation of RhB. Results demonstrate that the YBO3 microspheres were self-assembled by nanosheets. Compared with the YBO3 microparticles, redshift phenomenon appears at the absorption edge for YBO-85 with the formation of nanosheets structure. Meantime, the YBO3 microspheres have strong absorption in the ultraviolet range, higher photocurrent and less carrier migration resistance. So, YBO3 microspheres can exhibit a excellent activity to photodegrade RhB under UV light irradiation. The degradation rate of RhB can reach 90.9% under 40 min irradiation time.