Cubic phase MTiO3 (M=Ba or Sr) nanoparticle-supported TiO2 nanocomposites were prepared using Sr(OH)2 or Ba(OH)2 and TiO2 nanobelts as precursors by hydrothermal process. Their component, phase, morphology, structure and optical property were characterized using various XRD, SEM, TEM, HRTEM and UV-Vis techniques. The measurement results show that the more or less MTiO3 nanoparticles are affected by the amount of added Sr(OH)2 or Ba(OH)2 and the change in reaction time, and to some extent, the content of the MTiO3 is increased with the increase in the added hydroxide precursor and the prolonging of reaction time. Either the pure TiO2 nanobelts or the nanocomposites show the similar absorption and emission spectra. Their visible photodegradation activities of rhodamine B appear much higher than that of P-25.