A series of organic-inorganic hybrid films were prepared based on octa(3-chloropropylsilsesquioxane) (OCPS) and poly(L-lactic acid) (PLLA) via simply solution blending method. The thermal, crystalline and mechanical properties of OCPS/PLLA hybrid films were characterized by Fourier transform infrared, scanning electron microscopy, energy dispersive spectrometer, differential scanning calorimetry (DSC), X-ray diffraction, polarized optical microscopy, thermogravimetric analysis (TGA), and tensile tests. The results showed that OCPS could be dispersed well at molecular level when its content was less than 3 wt % and began to crystallize in PLLA matrix when the content increased to 5 wt %. DSC study revealed that OCPS acted as a plasticizer to decrease both T(g) and T(m) of the PLLA matrix at various heating rates. The addition of OCPS did not change the crystal form of PLLA, while had an great influence on the cold crystallization and melting behaviors of PLLA in the second heating cycles. Moreover, the initial crystallinity of OCPS/PLLA was higher than that of pure PLLA. The results suggested that OCPS could be an effective heterogeneous nucleating reagent to promote the crystallization of PLLA. TGA showed that the PLLA thermal degradation mechanism remained unchanged, whereas the weight loss temperatures and residual weights were improved. Tensile tests indicated that the incorporation of OCPS into PLLA matrix changed the tensile behavior of the hybrid films from brittle to ductile, and the strain at break was improved remarkably as a result of the plasticizer effect of OCPS. (c) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122: 296-303, 2011