Nanostructured Sr2Nb2O7 powders with different morphologies were synthesized via a hydrothermal reaction at 200 degrees C for 24 h in a Sr2+-Nb2O5.nH(2)O-KOH system. X-ray powder diffraction characterization indicated that 0.3-5M KOH solutions favored the formation of a Sr2Nb2O7 pure phase. On increasing the concentration of KOH from 0.3 to 5M, the morphology of Sr2Nb2O7 samples changed from nanoneedles to nanorods, nanosheets, and finally nano-sized flakes, and their aspect ratios gradually reduced. Ultraviolet-Visible diffuse reflectance spectra analyses showed that the nanostructured Sr2Nb2O7 powders had good light absorption properties in the ultraviolet light region.