BaSnO3 powders have been prepared from the tin oxide hydrate gel and the Ba(OH)(2) solution via hydrothermal synthesis route. The influence of the process parameters on the characteristics of BaSnO3 has been studied. A powder with the single-phase of BaSnO3 can be obtained only when the concentration of Ba(OH)(2) solution is no less than 0.2 M and the ratio of Ba:Sn lies between 1.0 and 1.2. At a hydrothermal temperature of 330 degrees C or higher, uniform BaSnO3 powders can be directly prepared through hydrothermal reaction. When the hydrothermal temperature is lower than 250 degrees C, the as-prepared powder consists of BaSn(OH)(6) that transforms through an amorphous phase into BaSnO3 by calcination at 260 degrees C. In the hydrothermal temperature range of 130-250 degrees C, a higher temperature can promote the crystallization of BaSnO3, increases its specific surface area and decreases the average particle size. The duration of the hydrothermal reaction affects the morphology of the powder particles. The effects of the nonaqueous solvents on the properties of powders have also been investigated.