Investigation of upconversion on nanocrystal and bulk La2O3 : (Yb3+, 1mol%Er3+ ) prepared by combustion and solid phase reaction was reported. Under 980 nm LD excition, predominant green upconversion(around 545 nm) in the bulk and strong red upconversion emission (around 660 nm) in the nanocrystal are obtained at room temperature. Under the same condition of measurement, the upconversion efficiency of the nanocrystal is lower than that of corresponding bulk, which mainly originates from the twophoton process for the nanocrystal and from energy transfer process between Yb3+ and Er3+ ions for the bulk.