By means of chemical combination between the Polydimethylsiloxane (PDMS) layer and Polyethersulfone (PES) layer, a kind of PDMS/PES composite membrane was prepared for separation of the light hydrocarbon components from the drilling mud. Meanwhile, its separation performance of the light-hydrocarbon components from the drilling mud was investigated and evaluated quantitatively. Results showed that the prepared PDMS/PES composite membrane had good mechanical performance, and it was resistant to corrosion of the water-based drilling mud. The PDMS/PES composite membrane can work stably at 5 MPa and 393 K. The responding time of the membrane to sudden change of the hydrocarbon gas content was less than one minute. For either single phase flow or gas-liquid two-phase flow, a high flow rate was recommended to avoid non-ideal flow patterns and to increase mass transfer in the feed channel of the membrane cell. Results in this work could be helpful for further application of the membrane technology in geological mud logging.