Gold (Au) was loaded on hydroxyapatite (HAP) supports with three different degree of crystallinity by deposition-precipitation method. Amorphous HAP and higher crystalline HAP nanoparticles were synthesized respectively by a direct precipitation process of which the aging time was 12 h or hydrothermal treatment at 180 degrees C. CO oxidation reaction was used to evaluate the behavior of catalysts. The physical properties of the catalysts were characterized by BET and TEM. The result found the catalyst with the lowest specific surface area had the highest initial activity. Patterns of XRD and XPS revealed that the HAP supports with higher crystallinity could produce more Au degrees over their surface which resulted in higher initial activity. This study suggested that the crystallinity of HAP supporter was another main factor to improve catalytic activity despite of specific surface area of the Au/HAP nanocatalysts. (C) 2014 Elsevier Ltd. All rights reserved.