Abstract: Hydroxyapatite (HA) coatings were prepared on carbon/carbon (C/C) composites by plasma spraying and tested by in vitro and in vivo methods. The Xray diffraction results indicated that the coatings consisted of HA, αtricalcium phosphate, and tetracalcium phosphate. The in vitro biological behavior of the HA coatings was studied in a Ringer solution. With increasing immersion time, new particles appeared on the surface of the coatings and these particles became bigger through agglomeration. In the days after the implantation, the experimental animals had no inflammation and rejection, and the coatings were firmly attached to the substrate. Histological observation showed that there was obvious bone tissue reconstruction on the surface of the coatings. In this light, the HA coatings plasmasprayed on C/C composites have excellent biological behavior and show promise as a bone repairing material.