Gd2O3：Ho^3＋,Yb^3＋ nanocrystals were synthesized via solvothermal method. X-ray diffraction （XRD）, transmission electron microscopy （TEM）, absorption and upconversion spectra were employed to characterize the synthesized nanocrystals. The results of XRD and TEM showed that obtained Gd2O3：Ho^3＋,Yb^3＋ nanocrystals were cubic in crystal structure and uniform spherical in morphology. The average crystallite size was calculated to be 7.5 nm. Green and red up-conversion emissions corresponding to （^5F4, ^5S2）→^5I8 and ^5F5→^5I8 transition were observed upon 980 nm excitation at room temperature. The results indicated that both green and red luminescence were based on the two-photon processes. Laser power and doping concentration dependence of the up- converted emissions were studied to understand the upconversion mechanisms. Excited state absorption and energy-transfer processes were discussed as the possible mechanisms for the visible emissions.
