A catalyst library consisting of 20 catalysts with different metal and weight fraction-doped TiO2 was prepared at one time for discovering the novel metal-doped TiO2 photocatalyst, which is active under visible light irradiation. Combinatorial microbeam XRD and UV-vis spectrometer were used for analysis of crystal structure and photoactivity of 20 catalysts in the library, respectively. Photodecomposition of phenol was chosen as a probe reaction. The library preparation, XRD characterization and reaction test for 20 catalysts were completed within 48 hours. Among the catalysts in the library, 1.5 wt% Co/TiO2 showed the best activity for phenol degradation.