A series of well-defined Ti-Si oxide composite spheres with hollow interior and porous shell wall were constructed through a complicated emulsion/interface method involving O/W/O structure present in the reaction system. The alternate Ti precursor of Ti ion solution (TIS) favors the composition homogeneity in the composite sphere shell by overcoming the mismatch hydrolysis ratio of the commonly chosen precursors, which is revealed by the fort-nation of Ti-O-Si bonds in SiO2 skeleton through XRD, Raman, Fr-IR, UV-vis analysis. This strategy is expected to extend to other composite preparation containing titanium composition. The resultant hollow Ti-Si oxide composite spheres from the emulsion droplets involving sacrificial organic cores exhibit variable sphere diameter in the range of ca. 10-500 mu m and tunable porous structure in sphere shell wall by deliberate control of the synthesizing parameters. The sleek inner and outer surfaces of the composite spheres proved by the broken ones originate from the sharp interface between organic and aqueous medium along with the existence of the non-ionic surfactant. (c) 2005 Elsevier B.V. All rights reserved.