Hydroxyapatite (HAp) has been synthesized by a hydrothermal treatment in the presence of a Gemini cationic surfactant. This process is a new strategy of synthesis and mainly consists of two parts, i.e., an ordinary hydrothermal treatment and a liquid-solid-solution reaction (LSS strategy). Crystalline HAp nanorods or nanogranules with length of 50-180 nm and width of 30-40 nm were produced by ordinary hydrothermal treatment. By contrary, HAp spheres with a 3D architecture were fabricated with Gemini cationic surfactant by LSS strategy. For Gemini cationic surfactant concentration of 0.05%, spherical HAp particles with an average diameter of 1.7 μm were obtained.