Abstract: A series of polyamide 66 (PA66)/polylactic acid (PLA) blends with different contents of PLA were prepared by a melt-blending method. The effect of PLA content on the fracture morphology, mechanical properties and crystalline properties of the blends after heat treatment were investigated. The results indicated that PA66 was partially compatible with PLA, and the blends achieved an increase in tensile strength by 93 % compared to pure PA66 when the content of PLA is less than 10 wt%. On the other hand, their elongation at break increased by a factor of 8.6 compared to PLA. The crystallization rate of PA66 increased and its crystallization time was shortened when less than 20 wt% of PLA was incorporated, indicating an improved crystalline property. Moreover, the tensile strength of the blends decreased significantly when the PLA content exceeded 20 wt%.