Abstract: The nano-hydroxyapatite (n-HA)/polylactic acid (PLA) composites, with n-HA mass fractions of 10%, 20%, 30% and 40%, respectively, were prepared using a twin-screw extruder. The dispersion of n-HA in the composite and the influence of n-HA content on the thermal property, viscosity and bending strength of the composite were researched. The results show that the n-HA with mass fractions of 10%-40% all dispersed relatively well in the PLA matrix. With the increase of n-HA content, the cold crystallization temperature and intrinsic viscosity of the n-HA/PLA composite decreased while the cold crystallization enthalpy and bending strength first increased and then decreased. When the mass fraction of n-HA was 10%, the n-HA/PLA composite had a good comprehensive performance, namely that the bending strength reached the largest value of 97.2 MPa and the damage degree of PLA molecular chain by n-HA was minimal.