Hydroxyapatite (HA) which has excellent biocompatibility and osteoconductivity is limited in the load-bearing repair because of its brittleness. Applying appropriate sintering additives for HA is a possible way to improve its mechanical properties. Systematic studies have has been performed to investigate the effect of LiCl as an additive on the microstructure and sinterability of HA and the relationship to its mechanical properties. The densification of HA containing different LiCl contents was completed through a special sintering process with the highest temperature of 1280°C. Microhardness was tested as a short cut to evaluate the changes of mechanical properties affected by the microstructure of HA doped with LiCl. The results of the experiment showed that LiCl is an effective sintering agent which causes neither decomposition of HA nor formation of other undesired phases with the increase of its microhardness.