The effect of Ca/P mole ratio (Ca/P=1.60, 1.67, 1.75) in the initial solution on the mechanical properties of alumina added hydroxyapatite was investigated. Hydroxyapatite was synthesized by precipitation method using Ca(NO3)2$.$4H2O and (NH4)2HPO4 as starting materials and 5 wt% of ${alpha}$-Al2O3 was added to precipitation solution. The powder was calcined at 800$^{circ}C$ and sintered at 1,150∼1,400$^{circ}C$ under water vapor atmosphere. With the increasing of Ca/P mole ration in the initial solution, the amount of tricalcium phosphate formed from the decomposition of hydroxyapatite reduced and the sinterability and mechanical properties were increased. The bending strength and Vickers hardness of the specimen sintered at 1,300$^{circ}C$ with the Ca/P mole ratio of 1.75 in the initial solution were 230 MPa and 650 kg/$ extrm{mm}^2$, respectively. The improvement of mechanical properties was attributed to not only the effect of Ca/P mole ratio but also the strengthening of sintered body by Al substitution for P ions.