To improve the thermal properties of linear low-density polyethylene (LLDPE), the CaCO3/LLDPE nanocomposites were prepared from nanometer calcium carbonate (nano-CaCO3) and LLDPE by melt-blending method. A series of testing methods such as thermogravimetry analysis (TGA), differential thermogravimetry analysis, Kim-Park method, and Flynn-Wall-Ozawa method were used to characterize the thermal property of CaCO3/LLDPE nanocomposites. The results showed that the CaCO3/LLDPE nanocomposites have only one-stage thermal degradation process. The initial thermal degradation temperature T0 increasing with nano-CaDO3 content, and stability of LLDPE change better. The thermal degradation activation energy (Ea) is different for different nano-CaCO3 content. When the mass fraction of nano-CaCO3 in nanocomposites is up to 10 wt %, the nanocomposite has the highest thermal degradation Ea, which is higher (28 kJ/mol) than pure LLDPE. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012