Nano titanium dioxide (TiO2) synthesized by sol-gel route was calcined at different temperatures, the powder calcined at 673 K indicates biphasic mixture of brookite and anatase. On the other hand the powder calcined at 773 K exhibited three phase mixture of anatase, brookite and rutile phases. The microstrain present in the multiphasic powder was studied by the X-ray diffraction Williamson - Hall method. Detailed Rietveld analysis with line profile analysis combined with spherical harmonics indicated the anisotropic microstrain in the calcined powders. The strain was found to reduce with calcination temperature. The anisotropic microstrain is correlated to oxygen vacancies, which influence the crystal structure parameters of the phases in terms of their TiO6 octahederal bond length/bond angle values. The bond valence sum analysis of the powders confirms for the oxygen vacancy in the titania powders.