A　nano-sized　powder　of　3%　(mole　fraction)　yttria　stabilized　tetragonal　zirconia　(3Y-TZP)　was　prepared　by　a　co-precipitation　method.　The　physical　and　chemical　properties　of　3Y-TZP　powders　were　characterized　by　X-ray　diffraction,　N2　adsorption-desorption　isotherms　and　transmission　electron　microscope,　respectively.　The　sintering　curve　of　the　nano-sized　powder　of　3Y-TZP,　the　densification　behavior　and　microstructure　of　the　sintered　bulk　were　analyzed,　and　the　influence　of　two-step　sintering　on　the　microstructure　of　the　3Y-TZP　ceramics　was　discussed.　The　results　show　that　the　well-developed　crystal　and　agglomeration-free　nano-sized　powder　with　the　grain　size　of　13　nm　was　obtained　by　co-precipitation　method　and　the　subsequent　calcination　at　600°C　for　2　h.　The　relative　density　of　the　3Y-TZP　ceramics　was　＞98%　and　the　grain　size　was　100　nm　when　the　green　body　was　calcined　at　1200°C　for　1　min　and　then　decreased　to　1050°C　for　35　h　using　two-step　sintering　method.　It　was　found　that　the　grain　growth　was　inhibited　and　the　densification　of　the　samples　was　achieved　through　controlling　the　calcining　temperature　and　holding　time　in　the　two-step　sintering　process　utilizing　the　different　migration　kinetics　between　the　grain　boundary　diffusion　and　the　grain　boundary　migration.　Finally,　the　sintered　body　had　a　full　density　without　any　grain　growth.