Biopolymer nanocomposite was synthesized using metal-free catalyst which is Montmorillonite-K10 as organic filler and acid catalyst for polymerization of L-Lactic acid. To evaluate the effect of Montmorillonite onto polymer properties, 1, 3 and 5% clay were used. Products were characterized using X-ray diffraction and transmission electron microscopy. Thermal parameters of products were investigated via differential scanning calorimeter and thermo-gravimetric analyzer. Thermal stability, degree of crystallinity, temperatures for glass transition, crystallization and melting of the nanocomposites were studied. Effect of clay onto molecular weight was investigated via gel permeation chromatography. It was found that properties of polymer were influenced by addition of clay.