In this work, the effects of pH on the formation of hydroxyapatite (HA) and Sr-substituted HA (Sr-HA) were studied. Calcium nitrate tetrahydrate and strontium acetate were dissolved in ethanol at the Ca:Sr mole ratio of 9.5:0.5. Diammonium hydrogen phosphate was dissolved in deionized water. The two solutions were mixed thoroughly and the ammonium solution was added in order to adjust the pH of the solution. After precipitation, the system was subjected to the heat until the dried powder was obtained and then calcined at 600°C for 2 h. From XRD study, HA was found as the main phase in all calcined powders. The substitution of Sr for Ca in HA structure was confirmed by the shift of XRD peak to lower angles and the shifts of OH to higher wave number and PO4 bands to lower wave numbers in FT-IR spectra.