In　this　paper,　mesoporous　hydroxyapatite　(HAp)　of　controllable　pore　size　was　tailored　with　the　template　of　a　biodegradable　mono-alkyl　phosphate　(MAP)　via　a　simple　route　by　hydrothermal　treatment.　A　serial　study　of　the　various　experimental　parameters　on　pore　size　of　HAp　was　investigated.　The　additive　amount　of　MAP　and　hydrothermal　temperature　were　important　factors　for　the　pore　structure　and　pore　size.　Powder　X-ray　diffraction　(XRD),　Fourier　transform　infrared　spectroscopy　(FTIR)　and　nitrogen　adsorption-desorption　(BET,　BJH)　were　used　to　characterize　the　structure　and　composition　of　the　HAp　samples.　Both　XRD　and　BJH　results　indicated　that　regular　mesoporous　HAp　nanoparticles　(with　a　mean　pore　size　of　3.5　nm)　were　successfully　produced.　As　shown　in　transmission　electron　microscopy　(TEM),　orderly　uniform　pore　structure　appeared　in　the　HAp　particles.　Because　of　the　special　structure　of　the　MAP　and　the　interaction　between　ionized　MAP　and　other　ions　in　solution,　the　product　presents　uniform　mesoporous　structure　with　well-defined　pore　size.　(C)　2015　Elsevier　B.V.　All　rights　reserved.