Tin-doped indium oxide (ITO) nanopowders with 90 +/- 3 and 40 +/- 3 nm particle size were prepared by the urea-based hydrothermal under a low-pressure method. The sintering behavior of the as-prepared ITO powder was studied at temperature from 1200 degrees to 1500 degrees C. The sintered ITO targets with large dimensions of 500 mm x 300 mm x 6 mm made from the as-prepared 90 and 40 nm powders with w(90 nm):w(40 nm)=70:30 had high density (99.7% of the theoretical density) and low specific electrical resistivity (120 mu center dot cm). The as-prepared powders were favorable to commercial fabrication of the high-density ITO targets.