Abstract: Rare-earth stannate (Ln₂Sn₂O₇ (Ln=Y, La-Lu)) nanocrystals with an average diameter of 50 nm were prepared through a facile microwave hydrothermal method at 200℃ within 60 min. The products were well characterized. The effect of reaction parameters such as temperature, reaction time, pH value, and alkali source on the preparation was investigated. The results revealed that the pH value plays an important role in the formation process of gadolinium stannate (Gd₂Sn₂O₇) nanoparticles. By contrast, the alkali source had no effect on the phase composition or morphology of the final product. Uniform and sphere-like nanoparticles with an average size of approximately 50 nm were obtained at the pH value of 11.5. A possible formation mechanism was briefly proposed. Gd₂Sn₂O₇:Eu³⁺ nanoparticles displayed strong orange-red emission. Magnetic measurements revealed that Gd₂Sn₂O₇ nanoparticles were paramagnetic. The other rare-earth stannate Ln₂Sn₂O₇ (Ln=Y, La-Lu) nanocrystals were prepared by similar approaches.