In this paper, by using the non-solvent induced phase separation (NIPS) process, a new microporous membrane with semi-interpenetrating polymer network (semi-IPN) was produced in which PDMS polymer is crosslinked and PVDF polymer is linear. For the fabrication of the membrane, tetraethylorthosilicate (TEOS) was used as the crosslinking agent and dibutyltin dilaurate (DBTDL) was used as the catalyst. By changing the mass ratio of PDMS/TEOS, the structure and the performance of the prepared membrane were studied. The membranes were also investigated by scanning electron microscopy (SEM-EDX), X-ray diffraction (XRD), attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, capillary flow porometer, thermogravimetric analysis (TGA), water contact angle (WCA), etc. Through the experiments we found that the semi-IPNs structure was more likely produce the sponge-like pores and was more favorable to the mechanical properties, pore structure and thermal stability of the membranes. Using the PDMS-PVDF membranes for the VMD desalt of the NaCl solution (30 g/L), 99.9% salt rejection and reasonable fluxes were obtained, which make us believe that it could be possible to use the semi-IPNs PDMS-PVDF membrane to treat real sea water for its desalt. POLYM. ENG. SCI., 57:1311-1321, 2017. (c) 2017 Society of Plastics Engineers