Ethanol perm-selective PDMS/PVDF composite membranes were prepared by curing polydimethylsiloxane (PDMS) with various cross-linking reagents, such as tetraethoxylsilane (TEOS),γ-aminopropyltriethoxylsilane (APTEOS), phenyltrimethoxylsilane (PTMOS) and octyltrimethoxylsilane (OTMOS) as well. The cross-linking density and surface properties of the PDMS active layer were adjusted by varying cross-linking reagents. The pervaporation performance of PDMS membranes cured with different cross-linking reagents was investigated in detail. As temperature increased, the total flux of the four kinds of membranes all increased exponentially, and the separation factor followed a reversed order. The increase of thickness of PDMS layers depressed the total flux of composite membranes and had no obvious effect on selectivity of ethanol. It was found that the composite membrane cured by PTMOS showed much better separation performance compared with other membranes. A resistance-in-series model was used to investigate and estimate the overall mass transfer coefficients and boundary layer mass transfer coefficients of ethanol and water according to experimental results. The measured diffusivities of ethanol and water in PDMS membranes had a magnitude of 10-10 m2．s-1 and 10-11 m2．s-1 at 313.15 K, respectively.