In this article, we report the fabrication of novel poly(L-lactide) (PLLA) nanocomposites based on PLLA and magnesium-aluminium layered double hydroxides (MgAl-LDH) which were mixed the polylactide with carboxyl end group (PLA-COOH) in acetone . Both the X-ray diffraction data and transmission electron microscopy images of the PLLA/LDH nanocomposites indicate that most of the LDH layers were disorderly exfoliated into the PLLA matrix. The thermal degradation behaviors of PLLA and its nanocomposites were studied using thermal gravimetric analysis (TGA) under nitrogen atmosphere at heating rates from 5 to 40 °C/min. The TGA profiles of the PLLA/LDH nanocomposites show less thermal stability than that of neat PLLA due to the presence of Mg and Al which has a drastic influence on thermal stability of PLLA. The activation energy of PLLA, 1 wt% and 3 wt% PLLA/LDH nanocomposites were 158, 140 and 130 kJ/mol, respectively.