Bioactive nano-titania ceramics with excellent biomechanical compatibility and bioactivity were prepared by using hydroxyapatite (HA) additive as grain growth inhibitor with different contents. After sintered at 1000 degrees C with pressureless sintering method, the grain size of nano-titania ceramic was less than 70 nm. Mechanical test results showed that compressive strengths of the nano ceramics were from 137.5 to 275.6 MPa, elastic moduli from 7 to 8 GPa, and bending strengths from 38.67 to 111.96 MPa by increasing HA additive content from 1 to 20%. The mechanical properties of nano-titania ceramics were analogous to that of the human bone. The content of HA additive played an important role in adjusting the grain/particle size of nano-titania ceramics, which had a great effect on the osteoblasts proliferation in the cell culture experiments. The cell culture experiments also demonstrated that the bioactive HA additive itself also had a great effect on the cytocompatibility of the nano-titania ceramics. The results of the present study indicated that the content of HA additive not only had effect on the bioactivity of the nano-titania ceramics because of the bioactivity of the additive itself, but also had effect both on the biomechanical compatibility and bioactivity of the nano-titania ceramics by adjusting the grain/particle size of the ceramics.