$Gd_2O_3$-doped $CeO_2$(GDC) solid solutions have been considered as a promising materials for electrolytes in intermediate-temperature solid oxide fuel cells. In this study, the nano-sized GDC powder with average panicle size of 69nm was prepared by a high energy ball milling process and its sintering behavior was investigated. Heat-treatment at $1200^{circ}C$ of nano-sized GDC powder mixture led to GDC solid-solution. The enhanced densification over 96% of relative density was obtained after sintering at $1300^{circ}C$ for 2h. It was found that the sinterability of GDC powder could be significantly improved by the introduction of a high energy ball milling process.