Anatase phase nanocrystalline TiO2 powders were prepared by hydrothermal method with the TTIP (titanium tetra isopropoxide) at 200 ℃ in a stirred autoclave system. The effects of synthesis conditions on the physical properties of catalyst were investigated by using XRD, SEM, DLS, DSC and BET. The TiO2 powders obtained from the optimum condition showed uniform spherical shape, crystalline structure, submicron size with a sharp size distribution and few agglomerates. The optimum synthesis conditions were obtained within the covered experimental ranges. The photocatalytic activity of TiO2 powders prepared by the hydrothermal method was tested for photooxidation of methyl orange.