In order to reduce the environmental hazard of waste oil water, the composite nanofibrous membranes were fabricated by electrospinning technique. The membranes were prepared by blending poly(lactic acid)/reduced graphene oxide (PLA/rGO) and hydroxyl-capped polydimethylsiloxane (HTPDMS) in varying ratios. The nanofibrous membranes were subjected to characterization by a scanning electron microscopy, an infrared spectroscopy, and a contact angle instrument to assess their micro-morphology, surface composition, and hydrophobicity. The results show that the addition of HTPDMS into PLA/rGO results in the formation of membranes consisting of nano-scaled fibres with HTPDMS. The hydrophobicity of PLA/rGO membrane is greatly improved by the addition of HTPDMS. The separation of oil-water mixtures has high oil fluxes, the fluxes are higher than 18 400 L/(m²·h), and the separation efficiency is greater than 98.2%. After 10 cycles of separation, the separation efficiency of fiber membrane can still reach more than 97%, with good cycle stability. PLA/rGO/HTPDMS fiber membrane has a broad application prospect in oily wastewater treatment.