Hydroxyapatite (HA) is one of the most widely used biomaterials for orthopedic and dental applications. However, HA is a brittle and weak material and this constrains its orthopedic applications. There are several methods for the improvement of mechanical properties of the HA. One of these methods is to strengthen the HA material by a secondary phase (i.e polymer, metal or ceramics), to make a stronger composite material. Alumina (Al2O3) is a bioinert material, which has been widely investigated as a reinforcing agent for HA. The aim of this study is to compare the microstructural and mechanical properties of HA-Al2O3 composites with the addition of 5 and 10 wt.% of commercial inert glass (GIG). The grain samples were produced according to BS 7253 at 350 MPa. Then, they were sintered at temperatures between 1000-1300 degrees C for 4 hours. The samples were also analyzed by SEM + EDS to determine microstructural properties, phase analysis was done by X-ray diffractometer (XRD), mechanical properties were measured by compression and hardness tests. Results show that HA-Al2O3 composites with addition of 5 and 10 wt.% GIG have reached high density values and high mechanical properties, such as compression strength and hardness at 1300 degrees C. The compression strength and hardness of composites has increased with the increasing GIG content.