The aim of this study was to develop a novel injectable hydroxyapatite for bone repair materials. This study was based on the in situ setting properties of calcium phosphate cement (CPC), which properties were improved. The solid phase consisted of tetracalcium phosphate (TTCP) and dicalcium phosphate anhydrous (DCPA). The liquid phase was the weak acidic solution of chitosan. The CPC powder was mixed with the chitosan solution to form a paste that could conform to the bone cavity even for irregularly shaped cavities. All the by-production disappeared by neutralization reaction. The CPC paste could then set in situ to form hydroxyapatite (HA) as the final product. The chemical process of CPC hydration was studied. The process was controlled by dissolution and precipitation chemical reaction. The kinetic model of hydration reaction was established. The effects of preparing conditions, such as powder to liquid ratio and particle size, on setting time and compressive strength were investigated systematically. The optimal condition was that the liquid phase contained 3% chitosan, 5% citric acid and 15% glucose (wt%), powder to liquid ratio was 0.8 g/ml, and powders were respectively ground for 40 hours.