Double-hydrophilic block copolymer (DHBC) poly-(vinylpyrrolidone)-b-poly(vinylpyrrolidone-alt-maleic anhydride)-b-poly-(vinylpyrrolidone) (PVP-b-P(NVP-alt-MAn)-b-PVP) was synthesised as the biomimetic template for the hydroxyapatite (HAP) nanocrystal synthesis. Needle-like HAP nanocrystals can be formed in the presence of PVP108-P(NVP-MAn)(28)-PVP108. Comparing to the HAP nanocrystals formed in the presence of poly-(vinylpyrrolidone) (PVP) homopolymer, the HAP nanocrystal formed with DHBC is more stable and never precipitate in water after preparation. The crystallization process and the morphology of the final nano-HAP crystal can be controlled by adjusting DHBC molecular structure.