Elongation, toughness, and barrier properties of PLA are not sufficient to use for many applications such as food packing and films. But, elongation, toughness and gas barrier can be improved by addingnanoclay in the PLA. Now, the most used Melt-Compounding Method is the twin-screw extruder because of productivity and continuity. The processing conditions such as screw configurations and screw speed determine the dispersions state of nanoclay in the matrix: hence affect the mechanical and barrier properties of PLA/clay nanocomposites. We prepared nanocomposites using three types of screw configulations with various screw speed. Dispersion state of nanoclays in the PLA was evaluated by TEM observation and rheology tests. It was found the screw configurations with mixing and blister elements showed the best in dispersion of clay. Furthermore, elongation of PLA nanocomposites increased from 5% to 15% with improving the dispersion state of nanocomposites. We confirmed that the processing consitions of twin-screw extruder was important to enhance the properties of PLA/clay nanocomposites.