Dense calcia-stabilized zirconia (CSZ) ceramics were prepared by using a small amount of boric acid (H₃BO₃) as the sintering additive at the sintering temperature of 1700°C. The effect of H₃BO₃ content on the sintering behavior, the change of phase composition and mechanical properties of the CSZ ceramics were mainly investigated. The results showed that, due to the reaction between B₂O₃ and CaO, borate liquid was formed during the sintering, which promoted the the densification of CSZ ceramics. Meanwhile, the depletion of the CaO from the lattice of CSZ ceramics resulted in the phase transformation of ZrO₂. The content of tetragonal ZrO₂ phase increased with increasing the H₃BO₃ content. So the phase composition of CSZ ceramics could be well controlled by adjusting the amount of H₃BO₃. The bending strength and fracture toughness of the sintered CSZ ceramics also increased with increasing the H₃BO₃ content, namely the content of tetragonal ZrO₂ phase, which had better mechanical properties, and the highest value reached 267 MPa and 3.35 MPa·m^1/2, respectively.