Various ratios of beta-Bi.sub.2O.sub.3/Bi.sub.2O.sub.2CO.sub.3 composites were successfully synthesized through solvothermal method which were characterized by XRD, UV-Vis DRS, SEM and XPS. The photocatalytic degradation of bisphenol A (BPA) demonstrated that both solvothermal and calcination temperatures significantly affected the photocatalytic activity of the prepared composites. The optimal photocatalytic performance was achieved at a solvothermal temperature of 180°C and a calcination temperature of 300°C under simulated sunlight irradiation with a 500 W xenon lamp. The characterization of the photocatalysts revealed that beta-Bi.sub.2O.sub.3/Bi.sub.2O.sub.2CO.sub.3 with diverse solvothermal temperatures exhibited a rose-like structure, and almost all materials possessed a wide absorption range from UV to visible light. A larger specific surface area is expected to provide more active sites and improve the photocatalytic activity of the materials. A narrower band gap would expedite the combination of e.sup.- and h.sup.+ and inhibit the photocatalytic process. The high photocatalytic activity of beta-Bi.sub.2O.sub.3/Bi.sub.2O.sub.2CO.sub.3 is primarily attributed to the phase transition from Bi.sub.2O.sub.2CO.sub.3 to beta-Bi.sub.2O.sub.3. In addition, the active species were detected by ESR with DMPO as a trap, and simultaneous trapping experiments were performed. The comprehensive analysis suggested that both h.sup.+ and ·O.sub.2.sup.- were the photocatalytically active species. The photocatalytic mechanism is proposed that the p-n heterojunction structure of beta-Bi.sub.2O.sub.3/Bi.sub.2O.sub.2CO.sub.3 accelerates the transfer of e.sup.- and h.sup.+.