Nanocrystals with orange-reddish luminescence based on the pyrochlore-type complete solid solutions with cube-like morphology in the Eu2Sn2O7-Gd2Sn2O7 system were directly formed from the precursor solutions of SnCl4, GdCl3, and EuCl3 under weakly basic hydrothermal conditions at temperatures higher than 180 degrees C for 5 h. The crystallite of Gd2Sn2O7 pyrochlore gradually grew from 10 to 37 nm as the hydrothermal treatment temperature rose from 180 degrees C to 240 degrees C. The lattice parameter of cubic phase linearly increased with increased europium concentration according to the Vegard's law. The characteristic orange-reddish photoluminescence spectra of Gd2Sn2O7:Eu3+ cubelike nanocrystals with crystallite size from 34 to 37 nm that were formed at 240 degrees C for 5 h were attributed to the most sharp orange (586 nm) luminescence with high intensity and quite broad red (610-630 nm) emission with weak intensity, according to the D-5(0) -> F-7(1) and D-5(0) -> F-7(2) transitions of Eu3+, respectively. At a composition of (Eu0.09Gd0.91)(2)Sn2O7, the intensity of orange emission reached the maximum. The Red-to-Orange (D-5(0) -> F-7(2)/D-5(0) -> F-7(1)) (R/O) emission intensity ratio was in the low range from 0.10 to 0.14, which was a characteristic of Gd2Sn2O7:Eu3+.