Abstract: The blends of polylactic acid (PLA) toughened by ethylene-1-octene copolymer (EOC) were prepared via molten blending and compress molding. The effects of the mass fraction of EOC on the morphology, mechanical and thermal properties were investigated. The results show that there was a little improvement in the interfacial compatibility between EOC and PLA with the in situ compatilization of maleic anhydride (MAH), exhibiting relative poor interfacial bonding. With the increment of EOC, the tensile strength and elastic modulus of EOC/PLA blends constantly decreased while the elongation at break and impact toughness increased and then declined, and their maximum values were obtained at 10wt.% and 20wt.% of EOC, respectively. There was no obvious variation on the thermal degradation of PLA phase after the blending of EOC and PLA, however a shifting of onset and maximum decomposition temperatures of EOC phase to high temperature zone was observed.