Poly (lactic acid) has a poor mechanical properties such as low elongation at break. In this paper, Poly (lactic acid) with epoxydized soybean oil were melted and mixed in Brabender internal mixer for 9 minutes at 190ºC to produce a ductile poly (lactic acid) with more elongation at break than poly (lactic acid). All functional groups of neat poly (lactic acid) and ductile poly (lactic acid) were investigated by FTIR analyzer. Mechanical properties such as tensile stress, elongation at break and young modulus of neat poly (lactic acid) and ductile poly (lactic acid) were investigated by Tensile strength test.